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Classifications

Harrison's Part

Mechanistic Nosology

ISDS Skeletal Nosology

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Inheritance

1

Autosomal Dominant HP:0000006

A single heterozygous loss-of-function LEMD3 allele is sufficient. Transmission is vertical, family history is the rule, and each child of an affected person has a 50% risk of inheriting the variant. Penetrance of the *syndrome* is hard to call complete because the two components are ascertained differently: a carrier with radiographically silent skin and no reason for an x-ray may look unaffected. Expressivity within a family is emphatically variable - relatives carrying the identical variant may have nevi alone, osteopoikilosis alone, or both - and no genotype-phenotype correlation has been established.

Autosomal dominant inheritance Penetrance: INCOMPLETE Expressivity: VARIABLE

Show evidence (3 references)

PMID:17087626 SUPPORT Human Clinical

"Autosomal dominant OPK and BOS feature widespread foci of osteosclerotic trabeculae without or with skin lesions, respectively."

States the autosomal dominant inheritance of both osteopoikilosis and Buschke-Ollendorff syndrome.

PMID:19438932 SUPPORT Human Clinical

"Our results further expand the LEMD3 mutation repertoire, corroborate the extreme interfamilial and intrafamilial clinical variability of LEMD3 mutations, and underline the lack of a clear phenotype-genotype correlation in BOS."

Directly supports variable expressivity within and between families and the absence of a genotype-phenotype correlation.

PMID:40195882 SUPPORT Human Clinical

"In addition, the fathers of probands 2 and 6 and the mother of proband 1, who all carry the same mutation as their offspring, did not present with BOS-related skin lesions upon physical examination."

Three obligate carriers in this series carried the proband's LEMD3 variant with no cutaneous manifestation, which is the clearest available demonstration that the skin component is not fully penetrant within a family.

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Subtypes

4

Complete Buschke-Ollendorff syndrome (nevi plus osteopoikilosis)

The full syndromic presentation: connective tissue nevi together with radiographic osteopoikilosis in the same individual. This was just over half of the cases in the 2016 systematic review.

Show evidence (1 reference)

PMID:26708699 SUPPORT Human Clinical

"Skin lesions were noted in 24% of cases and bony lesions in 20%, while 54% of patients had both."

Partitions reported BOS cases into skin-only, bone-only, and complete forms, and is the quantitative basis for treating the three as recognised presentations of one allelic disorder rather than as distinct diseases.

Skin-limited Buschke-Ollendorff syndrome (connective tissue nevi without osteopoikilosis)

Connective tissue nevi in a member of an LEMD3 kindred with no osteopoikilosis on radiographs. Some of this is genuine tissue-restricted expression and some is age-related: osteopoikilotic foci may not be radiographically apparent in early childhood, so a negative film in a young child does not settle the question.

Show evidence (2 references)

PMID:11298556 SUPPORT Human Clinical

"We present a family with Buschke-Ollendorff syndrome presenting as elastic tissue naevi without evidence of osteopoikilosis."

A whole family expressing the cutaneous component with no radiographic bone component.

PMID:40195882 SUPPORT Human Clinical

"Proband 3 and proband 5 had an X-ray examination of pelvis but did not exhibit any signs of OPK."

Two LEMD3-variant probands with cutaneous disease and negative pelvic radiographs.

Bone-limited expression (isolated osteopoikilosis in an LEMD3 kindred) MONDO:0015634

LEMD3 hgnc:28887

Radiographic osteopoikilosis with no connective tissue nevus, in a carrier of the family's LEMD3 variant. This is the same allelic disorder expressed in one tissue only, and it is how most silent carriers come to attention. The MONDO binding names the concept accurately but is a cross-reference rather than a claim that BOS subsumes sporadic isolated osteopoikilosis as an independent entity: MONDO places MONDO:0015634 under osteopoikilosis, not under Buschke-Ollendorff syndrome.

Show evidence (1 reference)

PMID:16470551 SUPPORT Human Clinical

"We confirm that loss-of-function mutations in the LEMD3 gene can result in either osteopoikilosis or BOS."

States that the same class of LEMD3 loss-of-function allele produces either the bone-only phenotype or the full syndrome, which is what makes bone-limited expression a subtype rather than a separate disease.

Buschke-Ollendorff syndrome with melorheostosis-like segmental hyperostosis MONDO:0015995

A minority of LEMD3 kindreds contain an individual with a large asymmetric area of dense cortical bone read as melorheostosis, superimposed on the symmetric osteopoikilotic foci. What converts one segment is unknown: no somatic second hit in LEMD3 has ever been demonstrated in such lesions. Distinguish this from sporadic isolated melorheostosis, which is a different disease - see the discussion entry "melorheostosis_attribution".

Show evidence (2 references)

PMID:17087626 SUPPORT Human Clinical

"In some OPK and BOS families, an individual may have relatively large, asymmetric areas of dense cortical bone interpreted as melorheostosis (MEL)."

Describes melorheostosis-like segmental hyperostosis as an occasional within-family manifestation of OPK/BOS.

PMID:17622481 SUPPORT Human Clinical

"The LEMD3 mutation reported was clearly the cause of osteopoikilosis in the two families but its relationship to melorheostosis in one of the family members is still unclear."

One family, one LEMD3 allele, and melorheostosis in only one member - the cleanest statement that the LEMD3 genotype alone does not determine the segmental lesion.

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Discussions and Knowledge Gaps

5

Is melorheostosis a manifestation of LEMD3 loss of function, or a separate disease that happens to look similar and occasionally co-occurs?

CONTROVERSY OPEN melorheostosis_attribution

Attached to

pathophysiology#Segmental Cortical Hyperostosis phenotypes#Melorheostosis has_subtypes#BOS with Melorheostosis

The 2004 gene-discovery paper put melorheostosis in its title alongside osteopoikilosis and BOS, and that framing persisted for years. It was wrong as a general claim, and the correction matters both nosologically and therapeutically. What is settled: (i) some individuals in LEMD3 kindreds do develop segmental cortical hyperostosis read as melorheostosis, and they carry the family's germline LEMD3 allele; (ii) patients with sporadic isolated melorheostosis - no osteopoikilosis, no family history - repeatedly test negative for germline LEMD3 variants, and negative for LEMD3 somatic mosaicism in lesional bone and skin; and (iii) most such patients instead carry a post-zygotic activating MAP2K1 variant confined to the affected bone, with mutant allele fractions of 1-34% and absent from contralateral unaffected bone and from blood. So sporadic melorheostosis is a somatic MEK1 mosaic disorder and is not BOS. What is not settled is the LEMD3-associated form. Within a kindred the germline allele is shared by everyone, yet only one member develops the segmental lesion, so the genotype alone cannot be the explanation. The long-standing hypothesis is a somatic second hit at LEMD3 in the affected segment, but that has been looked for and not found. Whether the LEMD3-associated segmental lesion is mechanistically the same entity as MAP2K1 melorheostosis, or a distinct lesion that resembles it radiographically, is unresolved - the two are convergent at the level of "excess cortical bone in an asymmetric focal pattern" and have not been compared histologically within one study. Curation consequence: this entry models the segmental hyperostosis as a within-syndrome node of hypothetical mechanism, keeps sporadic melorheostosis in differential_diagnoses rather than in the pathograph, and does not assert that LEMD3 causes melorheostosis in general.

Show evidence (6 references)

PMID:17087626 SUPPORT Human Clinical

"We confirm that OPK and BOS individuals, including those with MEL-like lesions, have heterozygous, deactivating, germline LEMD3 mutations. However, MEL remains of unknown etiology."

The study that separated the two claims - LEMD3 explains OPK/BOS including their MEL-like lesions, but not melorheostosis as an entity.

PMID:17087626 REFUTE Human Clinical

"However, no LEMD3 mutation was found for any other patient, including all four with sporadic MEL."

Refutes the proposition that LEMD3 loss of function explains sporadic melorheostosis - the claim carried in the 2004 paper's title.

PMID:19438932 REFUTE Human Clinical

"The present study supports the general conclusion that LEMD3 mutations do not contribute to isolated sporadic melorheostosis."

Independent replication of the negative LEMD3 result in isolated melorheostosis.

+ 3 more references

LEMD3 is expressed in essentially every nucleated cell and the loss-of-function allele is present in every cell. Why are the lesions confined to bone and dermis, and why are they focal within those tissues rather than uniform?

KNOWLEDGE GAP OPEN lemd3_tissue_selectivity

Attached to

pathophysiology#Increased BMP-SMAD1/5/8 Transcriptional Output pathophysiology#Dermal Fibroblast Elastin and Collagen Overproduction

This is the central unexplained feature of the disease and it has two parts. Tissue selectivity: a ubiquitous 50% reduction produces disease only where BMP and TGF-beta signalling sets matrix output - osteoblast lineage and dermal fibroblast. A plausible reading is that these are simply the tissues whose phenotype is most sensitive to SMAD dose, but that has not been tested; no BOS-specific transcriptomic, proteomic or single-cell dataset exists in any tissue. Focality within a tissue: this is the harder half. Cultured fibroblasts from clinically uninvolved BOS skin already overproduce tropoelastin more than three-fold, so the cellular defect is present where there is no lesion, and something else decides where a nevus forms. The same puzzle applies in bone, where the sclerotic nodules occupy a small fraction of a uniformly haploinsufficient skeleton. Two candidate explanations are on the table and neither has been tested in BOS tissue: a somatic second event confined to the lesion (searched for in LEMD3 and not found), or a local modifier such as matrix stiffness - the LEMD3-SMAD2/3 interaction weakens as stiffness rises, which would make the haploinsufficient cell progressively less able to restrain TGF-beta in exactly the stiffening matrix it is building, a plausible focal positive-feedback loop.

Show evidence (2 references)

PMID:1629625 SUPPORT In Vitro

"In a second patient, whose involvement was nearly complete, elastin production was high in involved areas and less so in completely involved skin."

Reports elastin production varying between skin sites within one patient, which is the observation the focality question rests on.

PMID:30108174 SUPPORT In Vitro

"Using human lung biopsies, we observed that these nuclear and cytosolic interactions are also present in tissue and found that fibrotic tissues exhibit locally diminished and cytoplasmically shifted LEMD3-SMAD2/3 interactions, as noted in vitro"

Shows locally diminished LEMD3-SMAD2/3 interaction in stiffened human tissue, the basis for the matrix-stiffness hypothesis offered here as one candidate explanation for focality.

What causes Buschke-Ollendorff syndrome in families with an unambiguous osteocutaneous phenotype and no detectable LEMD3 coding variant?

KNOWLEDGE GAP OPEN lemd3_negative_bos_families

Attached to

genetic#LEMD3

At least one family with textbook BOS - father and son with nevus elasticus plus radiographic osteopoikilosis - has been sequenced across all LEMD3 exons and splice sites with no variant found. Candidate explanations that have not been excluded include a deep intronic or regulatory variant, a copy-number change missed by sequencing (deletion/duplication analysis was not routine at the time), and locus heterogeneity involving another component of the nuclear-envelope SMAD-terminating machinery. The practical consequence is already established: a negative LEMD3 test does not overturn a convincing phenotype.

Show evidence (1 reference)

PMID:20083694 SUPPORT Human Clinical

"Although the clinical findings are diagnostic of Buschke-Ollendorf syndrome, analysis of the LEMD3 gene showed no exonic mutations."

The mutation-negative family that defines this gap.

Heterozygous Lemd3 mice have the same allelic state as human patients and show no skeletal phenotype at all. Is murine bone genuinely insensitive to Lemd3 dosage, or was the phenotype missed?

HUMAN MODEL MISMATCH OPEN bos_no_animal_model

Attached to

pathophysiology#Focal Trabecular Osteosclerotic Nodule Formation animal_models#Lemd3+/GT heterozygous gene-trap mouse

Human LEMD3 haploinsufficiency reliably produces osteopoikilosis. The heterozygous Lemd3 gene-trap mouse, examined by radiography, quantitative micro-CT histomorphometry across eight structural parameters, and conventional histology, showed nothing. The mismatch is not evidence-absent - the experiment was done and was negative - it is a translational validity problem, and it is the reason no animal model of the human bone phenotype exists. Alternatives that would discriminate: whether murine bone simply tolerates a halved dose (a real species difference in SMAD dose sensitivity), whether the murine lesion requires a longer lifespan or a mechanical challenge to appear, or whether the gene-trap allele is hypomorphic rather than null and the effective dose reduction was smaller than in patients. Until this is resolved, mechanistic and therapeutic hypotheses about the human lesion cannot be tested in vivo; a conditional or knock-in allele in the osteoblast lineage, or a patient-derived iPSC osteoblast system, is the obvious next step.

Proposed experiments

Osteoblast-lineage conditional Lemd3 inactivation

conditional_lemd3_osteoblast_lineage

Inactivate Lemd3 conditionally in the osteoblast/bone-lining lineage and age the animals, testing whether tissue-restricted and more complete loss produces focal sclerotic nodules that the germline heterozygote does not.

Would support

pathophysiology#Bone Lining Cell Activation and Modeling-Based Bone Formation

Supporting outcome

Discrete lamellar sclerotic nodules appear within trabecular bone on micro-CT, with modeling-based apposition and normal remodelling rate on dynamic histomorphometry, mirroring the human lesion.

Refuting outcome

No focal sclerosis develops even with complete lineage-restricted loss and ageing, which would move the explanation away from osteoblast-autonomous SMAD dose and toward a systemic or developmental requirement.

Show evidence (1 reference)

PMID:19862465 SUPPORT Model Organism

"To investigate whether the heterozygous gene-trapped mouse is a good model for osteopoikilosis in humans, we studied these mice radiologically with high-resolution micro-computed tomography (microCT) and histologically."

Describes the study design, establishing that the negative result comes from a purpose-built and adequately powered comparison rather than an incidental observation.

Is cognitive delay part of Buschke-Ollendorff syndrome, or an artefact of ascertainment and of contiguous 12q14 deletions being counted as BOS?

OPEN QUESTION OPEN bos_cognitive_delay_association

Attached to

phenotypes#Short Stature genetic#LEMD3

A 2016 systematic review reported cognitive delays in 50% of its own single-centre cohort and in 17% of literature cases published from 2007 onwards, with none reported before 2007. That temporal pattern is the problem: it is exactly what reporting bias looks like, and 2007 is also roughly when microarray testing became routine, so cases with a contiguous 12q14 deletion - which removes HMGA2 and other neighbours and does cause developmental delay and short stature - would have begun entering the BOS literature. A single-child 2024 preprint describing intellectual disability adds nothing decisive. No cognitive phenotype is deliberately curated in this entry's phenotypes block on this evidence. Resolving it needs neurodevelopmental assessment of a molecularly defined cohort with contiguous deletions excluded by array.

Show evidence (1 reference)

PMID:26708699 SUPPORT Human Clinical

"However, 50% of the cohort from HSC had cognitive delays, and only cases from 2007 onwards reported cognitive delays (the prevalence was 17% among those cases)."

The observation itself, including the post-2007 restriction that is the main reason to treat it as an ascertainment artefact rather than a syndrome feature.

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Pathophysiology

9

LEMD3 Haploinsufficiency

Mechanism confidence: Established

A heterozygous germline loss-of-function variant in LEMD3 - nonsense, frameshift, splice-disrupting, or whole-gene deletion - halves the functional dose of MAN1, a roughly 100-kDa integral protein of the inner nuclear membrane. Truncating alleles remove the C-terminal nucleoplasmic region that carries the SMAD-interacting module, so the residual protein cannot perform the function the wild-type allele is losing. No obligate somatic second hit has been found in lesional tissue, so the disorder is modelled as true haploinsufficiency rather than as a two-hit mosaic condition.

LEMD3 hgnc:28887

Genetic context LEMD3 hgnc:28887 variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Heterozygous germline truncating and deletion alleles across the LEMD3 coding sequence; reported examples include p.Y441X, p.L478X, p.R655X, p.W621X and p.Y871X, plus the frameshift c.332_333insTC.

inner nuclear membrane GO:0005637

Downstream

Loss of Nuclear Envelope R-SMAD Antagonism Reduced MAN1 dose at the inner nuclear membrane means fewer binding sites for receptor-activated SMADs, so less of the pathway-terminating activity MAN1 provides.

Show evidence (3 references)

PMID:15489854 SUPPORT Human Clinical

"All the affected individuals that we investigated were heterozygous with respect to a loss-of-function mutation in LEMD3 (also called MAN1), which encodes an inner nuclear membrane protein."

The gene-discovery study identifying heterozygous LEMD3 loss of function as the lesion, and MAN1 as an inner nuclear membrane protein.

PMID:15489854 SUPPORT Human Clinical

"A somatic mutation in the second allele of LEMD3 could not be identified in fibroblasts from affected skin of an individual with BOS and an individual with melorheostosis."

Negative search for a somatic second hit in lesional fibroblasts, which is why this node is modelled as haploinsufficiency rather than biallelic inactivation.

PMID:17087626 SUPPORT Human Clinical

"In the two BOS families, a heterozygous nonsense mutation (exon 1, c.1323C>A, p.Y441X) and a heterozygous frame-shift mutation (exon 1, c.332_333insTC) were identified."

Two independent BOS families with heterozygous truncating LEMD3 alleles, illustrating the variant classes involved.

Loss of Nuclear Envelope R-SMAD Antagonism

Mechanism confidence: Established

MAN1's C-terminal nucleoplasmic region binds the MAD homology 2 (MH2) domain of receptor-regulated SMADs at the inner nuclear membrane, in a ligand-independent manner and without binding the common mediator SMAD4. The interaction sequesters R-SMADs at the nuclear periphery and facilitates their dephosphorylation, so that the pathway is terminated rather than merely attenuated. Losing half of this capacity removes a brake, not a signal: nothing upstream of the receptor is altered, and the defect is in how quickly an activated SMAD is switched off. Recent work adds that the LEMD3-SMAD2/3 interaction is mechanosensitive, weakening as extracellular matrix stiffness rises, which offers one route by which a uniformly halved gene dose could produce focal rather than uniform lesions.

negative regulation of BMP signaling pathway GO:0030514 ↓ DECREASED negative regulation of TGF-beta receptor signaling pathway GO:0030512 ↓ DECREASED SMAD protein signal transduction GO:0060395

R-SMAD binding GO:0070412

inner nuclear membrane GO:0005637

Animal models

XMAN1 gain- and loss-of-function Xenopus embryo African clawed frog perturbs Bidirectional manipulation of MAN1 dose in a whole embryo, reading out BMP target gene expression, which is the mechanism this node asserts is lost in patients.

Downstream

Increased BMP-SMAD1/5/8 Transcriptional Output MAN1 binds SMAD1, SMAD5 and SMAD8; removing that binding leaves BMP-activated R-SMADs phosphorylated and transcriptionally competent for longer.

Increased TGF-beta-SMAD2/3 Transcriptional Output The same C-terminal module binds SMAD2 and SMAD3, so MAN1 loss equally releases the TGF-beta and activin arm.

Show evidence (3 references)

PMID:15647271 SUPPORT In Vitro

"MAN1, through the RNA recognition motif, associates with R-Smads but not Smad4 at the inner nuclear membrane in a ligand-independent manner."

Defines the physical interaction - R-SMADs but not SMAD4, at the inner nuclear membrane - that this node says is lost.

PMID:30321401 SUPPORT In Vitro

"MAN1 interacts with MAD homology 2 (MH2) domains of R-SMAD proteins using its C-terminal U2AF homology motif (UHM) domain and UHM ligand motif (ULM) and facilitates R-SMAD dephosphorylation."

Structural account of the interaction and of the terminating step - dephosphorylation of the R-SMAD - that MAN1 facilitates.

PMID:30108174 SUPPORT In Vitro

"We confirmed that a consensus C-terminal LEMD3 fragment binds SMAD2/3 in a stiffness-dependent manner throughout the cell and is sufficient for antagonizing SMAD2/3 signaling."

Shows the antagonism is modulated by matrix stiffness, the observation behind the note in this node's description that a uniform gene-dose defect might still act focally.

Increased BMP-SMAD1/5/8 Transcriptional Output

Mechanism confidence: Provisional

With MAN1 antagonism halved, BMP receptor activation yields more, and more prolonged, SMAD1/5/8-driven transcription. BMP signalling is the principal osteogenic input to the osteoblast lineage, so this is the arm that carries the skeletal phenotype. The direct measurement in human BOS tissue is still missing: the pathway effect is established in cell systems and in orthologue models, and its operation in patient osteoblasts is inferred.

BMP signaling pathway GO:0030509 ↑ INCREASED positive regulation of ossification GO:0045778 ↑ INCREASED

Downstream

Bone Lining Cell Activation and Modeling-Based Bone Formation Excess BMP-SMAD output in the osteoblast lineage is the proposed driver of the focal osteogenic response. The intermediate steps between a halved MAN1 dose and the recruitment of a particular patch of bone lining cells are not known, which is why the link type is INDIRECT_UNKNOWN_INTERMEDIATES rather than DIRECT.

Show evidence (2 references)

PMID:15489854 SUPPORT Human Clinical

"Osteopoikilosis, Buschke-Ollendorff syndrome (BOS) and melorheostosis are disorders characterized by increased bone density."

Frames the shared consequence of the LEMD3 lesion as increased bone density, the organism-level readout of this signalling arm.

PMID:12642484 SUPPORT INDIRECT Model Organism

"Importantly, XMAN1 antagonizes bone morphogenetic protein (BMP) signaling downstream of its receptor Alk3, as judged by animal cap assays, in which XMAN1 blocks expression of downstream targets of BMP signaling (Xhox3 and Msx1), and by luciferase reporter assays, in which XMAN1 suppresses..."

Demonstrates in vivo that MAN1 restrains BMP target-gene expression downstream of the receptor; its loss therefore raises BMP transcriptional output.

Increased TGF-beta-SMAD2/3 Transcriptional Output

Mechanism confidence: Provisional

The TGF-beta and activin arm is released in parallel. In dermal fibroblasts, TGF-beta is the dominant transcriptional stimulus for tropoelastin and fibrillar collagen, so this arm carries the cutaneous phenotype. The clearest human evidence is functional rather than transcriptional: fibroblasts cultured from BOS skin produce several-fold excess tropoelastin and carry elevated elastin mRNA, exactly the profile expected from unopposed TGF-beta drive.

transforming growth factor beta receptor signaling pathway GO:0007179 ↑ INCREASED extracellular matrix organization GO:0030198 ↕ DYSREGULATED

Animal models

Man1 Smad-interacting-domain homozygous deletion mouse Mouse partially recapitulates Loss of the Smad-interacting domain activates Smad2/3 signalling in vivo and increases extracellular matrix deposition, which is the molecular claim this pathophysiology node makes.

Downstream

Dermal Fibroblast Elastin and Collagen Overproduction TGF-beta1 is an established transcriptional inducer of tropoelastin in dermal fibroblasts, so unopposed SMAD2/3 output raises elastin and collagen synthesis.

Bone Lining Cell Activation and Modeling-Based Bone Formation TGF-beta acts on the osteoblast lineage as well, so the skeletal lesion is not attributed to the BMP arm alone. The relative contribution of the two arms to the bone phenotype has not been separated in human tissue.

Show evidence (2 references)

PMID:16943282 SUPPORT INDIRECT Model Organism

"We have demonstrated, in Man1-deficient embryos, the expression of Tgfb1 is upregulated and Smad2/3 signaling is abnormally activated, resulting in increased extracellular matrix deposition, a hallmark of the resolution phase of angiogenesis."

In vivo confirmation that losing MAN1's Smad-interacting domain activates Smad2/3 signalling and increases extracellular matrix deposition - the two claims this node makes - although in a homozygous mouse and in vascular rather than dermal tissue.

PMID:30108174 SUPPORT In Vitro

"We showed that LEMD3-SMAD2/3 interactions are inversely correlated with ECM stiffness and TGFβ-driven luciferase activity and that LEMD3 expression is correlated with the mechanical response of the TGFβ-driven luciferase reporter."

Ties LEMD3 level directly to the magnitude of TGF-beta-driven transcriptional output in human fibroblasts.

Bone Lining Cell Activation and Modeling-Based Bone Formation

Mechanism confidence: Established

Human bone biopsies from two women with LEMD3 variants show what the skeletal lesion actually is at the tissue level, and it is not accelerated remodelling. Overall bone turnover markers and remodelling rate were normal; instead, discrete areas of trabecular bone had been replaced by compact lamellar bone laid down by modeling-based formation - apposition on a quiescent surface, without a preceding resorption cavity - which implicates activation of bone lining cells. Woven bone was absent, so this is orderly lamellar deposition rather than a reactive or repair response.

bone lining cell CL:0000062 osteocyte CL:0000137

ossification GO:0001503 ↑ INCREASED bone mineralization GO:0030282

trabecular bone tissue UBERON:0002483

Downstream

Focal Trabecular Osteosclerotic Nodule Formation Modeling-based apposition within the marrow cavity and on the endocortex builds the discrete sclerotic noduli.

Segmental Cortical Hyperostosis In the minority of LEMD3 kindreds that show melorheostosis-like disease, the same osteogenic drive appears to act over a much larger, asymmetric cortical segment. What restricts and amplifies it there is unknown; see the "melorheostosis_attribution" discussion entry.

Show evidence (2 references)

PMID:32151766 SUPPORT Human Clinical

"These observations indicate that LEMD3 may be important for the activation of bone lining cells leading to modeling-based bone formation."

The authors' own mechanistic reading of their histomorphometry, and the basis for naming this node after bone lining cell activation.

PMID:32151766 SUPPORT Human Clinical

"Bone turnover markers were within normal range."

Excludes a generalised high-turnover state, which is why the node is framed as focal modeling rather than as systemic osteogenic overactivity.

Focal Trabecular Osteosclerotic Nodule Formation

Mechanism confidence: Established

The end-organ lesion of the bone arm: discrete, stellate to round nodules of compact lamellar bone, a few millimetres across, sitting within the trabecular cavity and on the endocortex, concentrated in epiphyses and metaphyses of long bones and in the pelvis, carpus and tarsus. They are metabolically quiet, do not remodel abnormally, and do not compromise the bone. Their broadly symmetric distribution is what distinguishes them radiographically from metastatic deposits.

trabecular bone tissue UBERON:0002483 bone element UBERON:0001474

Animal models

Lemd3+/GT heterozygous gene-trap mouse Mouse fails to recapitulate Heterozygous Lemd3 gene-trap mice form no osteopoikilosis-like sclerotic nodules on radiography, micro-CT or histology.

Downstream

Osteopoikilosis The nodules are the radiographic finding called osteopoikilosis.

Increased Bone Mineral Density Compact lamellar nodules are denser than the trabecular bone they replace, which is what raises regional bone mineral density.

Show evidence (2 references)

PMID:32151766 SUPPORT Human Clinical

"Woven bone was not observed in the nodules."

Establishes that the nodules are lamellar, not woven, which excludes a reactive or repair-type ossification and is a specific structural claim about this node.

PMID:26694706 SUPPORT Human Clinical

"Osteopoikilosis is a rare and benign autosomal dominant genetic disorder, characterized by a symmetric but unequal distribution of multiple hyperostotic areas in different parts of the skeleton."

Describes the symmetric but unequal skeletal distribution of the foci that this node produces.

Segmental Cortical Hyperostosis

Mechanism confidence: Hypothetical

A large, asymmetric, sharply demarcated region of dense cortical bone confined to one limb segment, radiographically the "flowing hyperostosis" or dripping-candle-wax pattern of melorheostosis. It occurs in a minority of LEMD3 kindreds, superimposed on osteopoikilosis. Unlike the osteopoikilotic nodules it can be symptomatic, with pain, deformity and joint restriction. This node deliberately makes no claim about the *sporadic* melorheostosis seen without osteopoikilosis, which is a different disease with a different mechanism.

bone element UBERON:0001474

Downstream

Melorheostosis The segmental cortical lesion is what is read on the radiograph as melorheostosis.

Show evidence (2 references)

PMID:17087626 SUPPORT Human Clinical

"MEL, however, classically refers to a sporadic, troublesome skeletal dysostosis featuring large, asymmetric, "flowing hyperostosis" of long bone cortices often with overlying, constricting soft tissue abnormalities."

Defines the radiographic and clinical character of the segmental cortical lesion modelled by this node.

PMID:30138550 SUPPORT Human Clinical

"A second subset of patients with germline mutations in LEMD3 and radiographic appearance of melorheostosis with coexisting familial osteopoikilosis has been described."

Establishes the LEMD3-associated, osteopoikilosis-accompanied form of melorheostosis as a recognised second subset, separate from the sporadic MAP2K1-driven form.

Dermal Fibroblast Elastin and Collagen Overproduction

Mechanism confidence: Established

Fibroblasts cultured from BOS skin produce two- to eight-fold more tropoelastin than normal dermal fibroblasts, and carry correspondingly elevated elastin mRNA - so the defect sits at or above the level of steady-state transcript abundance rather than in post-translational assembly. Notably the excess is not confined to clinically involved skin: apparently uninvolved skin from the same patient was elevated more than three-fold, which argues that the cellular defect is constitutive across the dermis and that something else localises the visible lesions. Collagen synthesis is altered in parallel, giving the collagen-rich lesions their character.

dermal fibroblast CL:0002551

elastic fiber assembly GO:0048251 ↑ INCREASED collagen fibril organization GO:0030199 ⚠ ABNORMAL

dermis UBERON:0002067

Downstream

Dermal Connective Tissue Nevus Formation Sustained matrix overproduction by dermal fibroblasts accumulates as the hamartomatous dermal deposit that is clinically a connective tissue nevus.

Show evidence (2 references)

PMID:1629625 SUPPORT In Vitro

"Cultured fibroblasts from both patients produced 2-8 times more tropoelastin than normal skin fibroblasts in the presence of 10% calf serum."

Quantifies the fibroblast overproduction of tropoelastin that defines this node.

PMID:1629625 SUPPORT In Vitro

"Involved skin fibroblasts of one patient produced up to eight times normal levels, whereas apparently uninvolved skin was also elevated more than threefold."

Supports the statement that the cellular defect extends to clinically normal skin, which is the observation behind treating lesion localisation as unexplained.

Dermal Connective Tissue Nevus Formation

Mechanism confidence: Established

Accumulated matrix forms a hamartomatous dermal nodule. Histology is heterogeneous and this is the practically important point: the classic lesion is an elastoma, with large, thickened, haphazardly arrayed elastic fibres visible on Victoria blue or other elastic stains, but a substantial minority are collagenomas of dense hypocellular collagen with normal elastic tissue, some are mixed, and increased interstitial dermal mucin is common and easily missed. A biopsy read as unremarkable on routine haematoxylin and eosin therefore does not exclude BOS, and two lesions from the same patient at different body sites can look different.

dermis UBERON:0002067 skin of body UBERON:0002097

Downstream

Connective Tissue Nevi The dermal deposit is what presents clinically as a connective tissue nevus.

Collagenoma Where the accumulated matrix is predominantly collagen, the lesion is classified as a collagenoma.

Increased Number of Elastic Fibers in the Dermis Where elastic tissue predominates, the deposit presents as thickened, increased and disordered dermal elastic fibres - the elastoma pattern.

Show evidence (2 references)

PMID:32206820 SUPPORT Human Clinical

"Two skin lesion patterns have been described because they may be of either elastic tissue (juvenile elastoma) or collagenous composition (dermatofibrosis lenticularis disseminata)."

States the elastoma versus collagenoma division of the dermal lesion that this node describes.

PMID:40195882 SUPPORT Human Clinical

"Notably, biopsies from a plantar foot nodule and a buttock nodule in proband 3 presented differing histological features, suggesting that lesion location may influence pathological presentation, even within the same individual."

Supports the claim that histology varies by site within one patient, not only between patients.

✶

Histopathology

4

Dermal Elastoma FREQUENT

The classical BOS dermal lesion. Elastic-tissue stains (Victoria blue, Verhoeff-van Gieson, orcein) show markedly increased, thickened, broad and irregularly arranged elastic fibres filling the reticular dermis. No term in the NCIT histopathology branch or under HP Abnormal cell morphology names this lesion, so finding_term carries a free-text preferred_term only; the corresponding HP phenotype (HP:0025164) is bound in the phenotypes block instead.

Show evidence (1 reference)

PMID:40195882 SUPPORT Human Clinical

"Histologically, elastoma is traditionally regarded as the predominant feature of BOS."

States the primacy of the elastoma pattern among BOS dermal biopsies.

Dermal Collagenoma OCCASIONAL

Dense, hypocellular, haphazardly interlacing collagen bundles expanding the dermis with normal or reduced elastic tissue, demonstrated on Masson trichrome. May be the only pattern present, and may coexist with elastoma in the same patient at different sites.

Show evidence (1 reference)

PMID:40195882 SUPPORT Human Clinical

"Masson's trichrome staining indicated collagenoma in probands 3 (foot) and 4 (Fig. S1A)."

Documents collagenoma by trichrome staining in two genetically confirmed probands.

Interstitial Dermal Mucin Deposition FREQUENT

Increased interstitial mucin between the dermal collagen and elastic fibres, demonstrated on Alcian blue. Under-recognised: it was present in every proband of the 2025 series, and in at least one reported child it was the only abnormality on an otherwise unremarkable biopsy. Its mechanistic relation to LEMD3 loss is unknown.

Show evidence (2 references)

PMID:40195882 SUPPORT Human Clinical

"Alcian blue staining demonstrated increased interstitial mucin in the reticular dermis of all probands (Fig. S1A)."

Establishes dermal mucin as a consistent finding in this series.

PMID:32206820 SUPPORT Human Clinical

"A skin biopsy was performed and did not show striking alterations in the number or dimension of the extracellular matrix fibers, but it showed mucin deposition between them, which is compatible with a CTN."

A case in which mucin was the only histological abnormality, supporting the warning that a fibre-normal biopsy does not exclude a connective tissue nevus.

Compact Lamellar Sclerotic Bone Nodule

On undecalcified bone histology and micro-CT the osteopoikilotic focus is a stellate nodule of compact lamellar bone within the marrow cavity or on the endocortex, formed by modeling-based apposition. Remodelling rate is normal and woven bone is absent. The NCIT binding is the generic morphologic finding "Sclerosis"; NCIT has no term for this specific lesion.

Show evidence (1 reference)

PMID:32151766 SUPPORT Human Clinical

"In both biopsies, μCT showed trabecular structure comparable to that of controls with stellate shaped sclerotic noduli within the cavity and on the endocortex."

Describes the stellate sclerotic nodules and their position within otherwise normal trabecular bone.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

10

Integument 4

Connective Tissue Nevi FREQUENT HP:0100898

Show evidence (2 references)

PMID:26708699 SUPPORT Human Clinical

"BOS commonly presents with nontender connective tissue naevi and sclerotic bony lesions (osteopoikilosis [OPK])."

Establishes connective tissue nevi as one of the two cardinal presenting features.

PMID:40195882 SUPPORT Human Clinical

"Clinically, all 6 probands presented with multiple yellowish to red papules and nodules, some of which coalesced into cobblestone-like nevoid plaques (Fig. 1A)."

Describes the morphology and coalescence pattern of the nevi in a genetically confirmed series.

Increased Number of Elastic Fibers in the Dermis FREQUENT HP:0025164

Show evidence (1 reference)

PMID:40195882 SUPPORT Human Clinical

"Victoria blue staining revealed that the dermis of probands 2, 3 (buttocks), 4, 5, and 6 exhibited large, thickened, and haphazardly arrayed elastic fibres (Fig. S1A)."

Documents the increased, thickened, disordered dermal elastic fibres in five of six genetically confirmed probands.

Collagenoma OCCASIONAL HP:6000022

Show evidence (1 reference)

PMID:40195882 SUPPORT Human Clinical

"Nevertheless, an examination of reported histological manifestations in BOS cases reveals that 8% of cases exclusively presented with collagenoma, while 23% displayed a mixed phenotype encompassing both collagenoma and elastoma."

Quantifies collagenoma-only and mixed lesions across the reported literature.

Yellow Papule FREQUENT HP:0025507

Show evidence (2 references)

PMID:20083694 SUPPORT Human Clinical

"We describe a father and son with multiple yellowish papules and nodules coalescing into cobblestone nevoid plaques consistent with nevus elasticus."

Describes the yellowish papular morphology and its coalescence into nevoid plaques.

PMID:18986450 SUPPORT Human Clinical

"Physical examination of the patient showed multiple asymptomatic nodules on both thighs, present since the age of 20 years, which had increased in size and number."

Illustrates the asymptomatic, slowly accumulating course of the cutaneous lesions.

Musculoskeletal 4

Osteopoikilosis FREQUENT HP:0010739

Sequelae: Arthralgia

Show evidence (2 references)

PMID:17087626 SUPPORT Human Clinical

"BOS combines OPK with connective tissue nevi comprised of collagen and elastin."

Defines osteopoikilosis as the skeletal half of the syndrome.

PMID:40195882 SUPPORT Human Clinical

"OPK is another defining characteristic of BOS; a summary of OPK locations revealed that the pelvis is the most commonly affected site."

Supports the distribution claim, with the pelvis as the commonest site across reported cases.

Increased Bone Mineral Density FREQUENT HP:0011001

Show evidence (1 reference)

PMID:32151766 SUPPORT Human Clinical

"aBMD Z-scores were comparable to that of controls in the lumbar spine and increased at the hip."

Quantifies the densitometric picture and supports the qualification that the increase is regional rather than generalised.

Melorheostosis OCCASIONAL HP:6000817

Show evidence (1 reference)

PMID:17087626 SUPPORT Human Clinical

"Occasionally, a larger area of dense bone in OPK or BOS resembles MEL, a sporadic sclerosing disorder primarily involving cortical bone."

Establishes melorheostosis-like cortical disease as an occasional finding in OPK and BOS.

Spinal Canal Stenosis VERY_RARE HP:0003416

Show evidence (1 reference)

PMID:26708699 SUPPORT Human Clinical

"All patients with spinal stenosis (2%) or shortened status (7%) had OPK."

Source of the 2% spinal stenosis figure among reported BOS cases.

Constitutional 1

Arthralgia OCCASIONAL HP:0002829

Show evidence (1 reference)

PMID:25352085 SUPPORT Human Clinical

"Although it is usually asymptomatic, effusion and joint pain can be found in 15-20 % of patients."

Source of the 15-20% figure for joint symptoms in osteopoikilosis.

Growth 1

Short Stature OCCASIONAL HP:0004322

Show evidence (1 reference)

PMID:26708699 SUPPORT Human Clinical

"All patients with spinal stenosis (2%) or shortened status (7%) had OPK."

Source of the 7% figure and of the observation that it co-occurs with the bone component.

🧬

Genetic Associations

1

LEMD3 (Causative; heterozygous germline loss of function)

Gene: LEMD3 hgnc:28887 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (4 references)

PMID:15489854 SUPPORT Human Clinical

"A genome-wide linkage analysis in these families, followed by the identification of a microdeletion in an unrelated individual with these diseases, allowed us to map the gene that is mutated in osteopoikilosis."

The mapping and gene-identification step that established LEMD3 as causative.

PMID:27382493 SUPPORT Human Clinical

"Two additional family members were found to have osteopoikilosis and carry the same LEMD3 mutation."

Cosegregation of an LEMD3 nonsense allele with osteopoikilosis across a family.

PMID:26694706 SUPPORT Human Clinical

"The mutation co-segregates with the osteopoikilosis phenotype and was not found in 100 ethnically matched controls."

Cosegregation across three generations with control screening, supporting causality of truncating LEMD3 alleles.

+ 1 more reference

💊

Medical Actions

6

Observation and Reassurance

Action: supportive care Ontology label: Supportive Care NCIT:C15747

For the great majority of patients this is the whole of management. Osteopoikilotic foci are benign, non-progressive and asymptomatic and require no intervention, and most connective tissue nevi need none either. The active work is explaining the radiographic findings so that neither the patient nor a future clinician mistakes them for malignancy, and documenting the diagnosis where it will be found again.

Show evidence (1 reference)

PMID:17087626 SUPPORT Human Clinical

"OPK is an autosomal dominant, usually benign, skeletal dysplasia featuring multiple, small, especially metaphyseal, oval or round, dense trabecular foci distributed symmetrically throughout the skeleton."

Establishes the benign nature of the skeletal lesions that justifies observation over intervention.

Genetic Counselling and Cascade Evaluation

Action: Genetic Counseling NCIT:C15240

Autosomal dominant transmission with a 50% recurrence risk per pregnancy, but counselling must convey that the phenotype in an inheriting child cannot be predicted from the parent's: the same allele produces skin-only, bone-only, full and clinically silent presentations within one family. Cascade radiographic and dermatological evaluation of relatives is useful mainly to spare them an oncological workup later. Because the causative gene is known, prenatal diagnosis and preimplantation genetic testing are technically available once a familial LEMD3 variant has been identified; counselling should say so while setting it against the condition's generally benign course and the fact that the severity in an inheriting child cannot be predicted, so the decision is not the one it would be for a progressive or life-limiting disease.

Show evidence (1 reference)

PMID:19438932 SUPPORT Human Clinical

"We investigated LEMD3 in a two-generation BOS family showing an extremely variable expression of the disease, in a sporadic patient with skin features of BOS, and in an additional subject with isolated melorheostosis."

Documents the extreme within-family variability that counselling has to convey.

Analgesic Therapy for Musculoskeletal Pain

Action: Pharmacotherapy NCIT:C15986

Agent: analgesic agent NCIT:C241

Platform: Small molecule

Simple analgesics or anti-inflammatory agents for the minority who have joint pain or effusion, or pain from a melorheostotic segment. Symptomatic only; no agent modifies the underlying bone lesion.

Target Phenotypes: Arthralgia HP:0002829

Show evidence (1 reference)

PMID:25352085 SUPPORT Human Clinical

"Although it is usually asymptomatic, effusion and joint pain can be found in 15-20 % of patients."

Establishes the minority with joint symptoms who need analgesia; the paper does not specify a regimen.

Surgical Excision of Symptomatic Connective Tissue Nevi

Action: surgical excision Ontology label: Excision NCIT:C15232

Platform: Surgery

Excision may be considered for a nevus that is painful, mechanically limiting (hand and plantar lesions in particular) or cosmetically distressing. Counsel about scarring first: hypertrophic scarring after skin incision was recorded in four of six probands in the 2025 series, and in one reported case the excision itself produced a disabling contracture. Outcome evidence is limited to case reports.

Show evidence (2 references)

PMID:40195882 SUPPORT Human Clinical

"Notably, 4 probands developed scars after skin incisions (Fig. 1A)."

The scarring risk that has to be weighed before excising a benign lesion.

PMID:27267960 SUPPORT Human Clinical

"Two sclerotic skin lesions had been excised 7 years before because of consecutive skin contracture."

A reported case in which excision was undertaken for contracture, illustrating both the indication and the sequela.

Corrective Orthopaedic Surgery

Action: orthopaedic surgical procedure Ontology label: Orthopedic Surgical Procedure NCIT:C16186

Platform: Surgery

Reserved for substantial fixed deformity, joint impingement or nerve entrapment, which in practice means the melorheostotic rather than the osteopoikilotic skeleton. Reported interventions include corrective osteotomy for a digital deformity. Contracture recurrence after soft-tissue surgery in extensive melorheostosis is a recognised problem.

Show evidence (2 references)

PMID:27267960 SUPPORT Human Clinical

"A corrective osteotomy of the thumb was carried out due to the patients discomfort."

A reported corrective osteotomy in a genetically confirmed BOS patient.

PMID:30989250 SUPPORT Human Clinical

"Surgical intervention may be required for those with large bone growths, nerve entrapments, joint impingement syndromes or major limb deformities."

Sets out the indications for surgery in the melorheostotic subset.

Bisphosphonate Therapy for Symptomatic Melorheostosis

Action: bisphosphonate therapy Ontology label: Bisphosphonate Therapy NCIT:C198585

Platform: Small molecule

Used for pain in symptomatic melorheostosis, on weak evidence. Not indicated for osteopoikilosis or for the cutaneous lesions, and there is no reason to expect benefit there - the osteopoikilotic nodule has a normal remodelling rate, so an antiresorptive has no obvious target. Included because it is the one pharmacological option that appears in the sclerosing-bone-disease literature; it is not BOS therapy.

Target Phenotypes: Melorheostosis HP:6000817

Show evidence (1 reference)

PMID:30989250 SUPPORT Human Clinical

"Medical treatments include bisphosphonates, but definitive guidance on their use is lacking given the small number of patients that have been studied."

Supports both the use and the explicit weakness of the evidence base for it.

🔬

Diagnosis

4

Clinical and Radiographic Diagnosis

BOS is diagnosed from the combination of connective tissue nevi and radiographic osteopoikilosis, usually with a supporting family history. Plain radiographs of the pelvis, hands and wrists, knees and ankles are the highest-yield screen; CT adds little in typical disease and PET/MRI is unnecessary. Because expressivity is variable, a first-degree relative with only one component still warrants consideration, and a negative childhood radiograph does not exclude osteopoikilosis that appears later.

plain radiography NCIT:C38101

Show evidence (2 references)

PMID:26708699 SUPPORT Human Clinical

"A family history was noted in 92% of cases."

Supports the weight given to family history in recognising the syndrome.

PMID:18986450 SUPPORT Human Clinical

"After a minor trauma, radiologic examination of the left ankle of a 39-year-old woman revealed features of osteopoikilosis."

Illustrates the typical route to diagnosis - an incidental radiograph taken for an unrelated reason.

Bone Scintigraphy to Exclude Osteoblastic Metastasis

The clinically consequential mistake in this disease is reading the sclerotic foci as osteoblastic metastases and launching an oncological workup. Radionuclide bone scanning resolves it: osteopoikilotic foci are cold, metastatic deposits are avid. This is the highest-value single investigation when the radiographic finding is encountered without a known diagnosis.

radionuclide bone scan NCIT:C17646

Show evidence (2 references)

PMID:25352085 SUPPORT Human Clinical

"It may be confused with other conditions, such as osteoblastic metastases."

Names the differential this investigation exists to settle.

PMID:27267960 SUPPORT Human Clinical

"A correct diagnosis of Buschke-Ollendorff syndrome is necessary to spare patients from expensive investigations and to provide reassurance about the benign nature of the disease."

States the clinical value of arriving at the diagnosis - avoiding unnecessary investigation.

Skin Biopsy with Elastic-Fiber and Mucin Staining

Reserved for atypical or diagnostically uncertain lesions. Request elastic-tissue staining (Victoria blue, Verhoeff-van Gieson or orcein), trichrome and Alcian blue alongside routine histology: routine haematoxylin and eosin alone can look unremarkable, and the pattern may be elastoma, collagenoma, mixed, or mucin-rich. A non-classic biopsy therefore does not exclude the diagnosis.

skin biopsy NCIT:C51692

Show evidence (1 reference)

PMID:40195882 SUPPORT Human Clinical

"These results underscore the pathological heterogeneity of BOS."

Supports ordering the full panel of stains rather than relying on a single classic pattern.

LEMD3 Molecular Genetic Testing

Sequencing of the LEMD3 coding exons and splice boundaries confirms the diagnosis and enables cascade testing of relatives; deletion/duplication analysis should be added, since whole-gene deletions occur. A negative result does not overturn a convincing osteocutaneous phenotype - genetically unexplained BOS families are documented. Screening is specifically recommended in atypical presentations that combine fibrotic skin lesions with a spotted radiographic pattern.

LEMD3 sequence analysis NCIT:C19770

Show evidence (1 reference)

PMID:27267960 SUPPORT Human Clinical

"In atypical cases of simultaneous occurrence of fibrotic skin lesions and a spotted pattern in the X-ray we recommend the genetic screening of the LEMD3 gene."

Explicit recommendation for LEMD3 screening in the presentation this entry describes.

🩻

Imaging Findings

3

Multiple Symmetric Periarticular Sclerotic Foci

The diagnostic plain-film appearance: numerous small, well-defined, homogeneous round or ovoid densities clustered around joints and distributed broadly symmetrically. Pelvis, hands and wrists, knees and ankles are the highest-yield films. Their uniformity and symmetry are what separate them from osteoblastic metastatic deposits, which are irregular, asymmetric and axially predominant.

Xray Diagnostic Multifocal

Osteopoikilosis HP:0010739

Show evidence (1 reference)

PMID:25352085 SUPPORT Human Clinical

"OPK must be in differential diagnosis when multiple, small, well-defined, symmetric bone lesions are identified on plain radiograph to avoid alarming the patient with more serious disease and misdiagnosis."

Describes the radiographic pattern and states the clinical reason it matters.

Normal Bone Scintigraphy Over Osteopoikilotic Foci

Radionuclide bone scanning is normal over osteopoikilotic foci, consistent with the histological finding of normal remodelling rate, and this is the single most useful discriminator from osteoblastic metastases, which are avid. Note the contrast with the melorheostotic lesion, which is metabolically active and does show uptake.

Other

normal radionuclide bone scan over sclerotic foci

Show evidence (1 reference)

PMID:25352085 SUPPORT Human Clinical

"Bone scintigraphy is normal and useful for differential diagnosis."

Establishes normal scintigraphy as the discriminating investigation.

Flowing Cortical Hyperostosis

Where melorheostosis accompanies BOS, radiographs show dense, irregular, eccentric hyperostosis of the cortex in a segmental distribution, classically likened to dripping candle wax, with sharp demarcation between affected and unaffected bone.

Xray Segmental

Melorheostosis HP:6000817

Show evidence (1 reference)

PMID:30138550 SUPPORT Human Clinical

"Melorheostosis is a rare hyperostotic disease of the long bones classically characterized by a "dripping candle-wax" radiographic appearance."

Defines the radiographic appearance this finding records.

📊

Prevalence

2

Worldwide

Unknown 5.0 per 100,000 1–9 per 100,000

The frequently repeated figure is approximately 1 in 20,000, i.e. 5 per 100,000. It is recorded here as measure_type UNKNOWN rather than as an incidence or a point prevalence: the source states it as an "estimated incidence" but supplies neither a denominator population nor an observation period, and it traces back through the case-series literature rather than to a registry. Ascertainment is certainly incomplete in both directions - osteopoikilosis is asymptomatic and found incidentally, and the cutaneous nevi are easily dismissed as unremarkable papules - so the true figure could lie either side. No population-based BOS prevalence study was identified.

Show evidence (1 reference)

PMID:40195882 SUPPORT Human Clinical

"initially described by Buschke and Ollendorff in 1928, is a rare autosomal dominant genetic disease with an estimated incidence of 1 in 20,000"

Source of the 1-in-20,000 figure. The paper cites it to earlier literature rather than deriving it, which is why the measure type is left UNKNOWN here.

Published Buschke-Ollendorff syndrome case reports (systematic review of 164 cases)

Cases In Literature Ultra Rare

A 2016 systematic review recovered 164 reported cases from 48 publications with no date or language restriction, which bounds the size of the published literature rather than the size of the affected population.

Show evidence (1 reference)

PMID:26708699 SUPPORT Human Clinical

"In total, 594 reports were discovered, of which 546 (92%) were excluded. The remaining 48 accounted for 164 cases."

Quantifies the entire published case literature for this disorder as of 2016.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Buschke-Ollendorff Syndrome:

Osteoblastic Bone Metastases

Overlapping Features The differential that matters. Metastatic osteoblastic deposits are irregular, asymmetric, axially predominant and scintigraphically avid; osteopoikilotic foci are uniform, periarticular, broadly symmetric and cold on bone scan.

Distinguishing Features

Symmetric periarticular distribution versus irregular axial distribution
Normal bone scintigraphy versus increased radiotracer uptake
Stable over decades versus progressive
Family history of the same radiographic pattern

Show evidence (1 reference)

PMID:25352085 SUPPORT Human Clinical

"Diagnosis is usually made incidentally according to radiographs."

Supports the framing that this differential is typically encountered on an incidentally obtained film.

Sporadic Isolated Melorheostosis

Overlapping Features Melorheostosis without osteopoikilosis, occurring sporadically without familial clustering. This is a genetically distinct disease driven by post-zygotic activating MAP2K1 mutation restricted to the affected bone, not a forme fruste of BOS. Repeated LEMD3 sequencing of such patients - including of lesional bone and skin - has been negative.

Distinguishing Features

No connective tissue nevi and no osteopoikilotic foci elsewhere in the skeleton
Sporadic occurrence with no family history
Somatic mosaic MAP2K1 variant in affected but not unaffected bone
Germline LEMD3 sequencing negative

Show evidence (2 references)

PMID:29643386 SUPPORT Human Clinical

"Using whole exome sequencing, we identify somatic mosaic MAP2K1 mutations in affected, but not unaffected, bone of eight unrelated patients with melorheostosis."

Establishes the distinct somatic MAP2K1 aetiology of sporadic melorheostosis.

PMID:16470551 SUPPORT Human Clinical

"Somatic mosaicism for a LEMD3 mutation in the latter group was also not observed, and therefore we must conclude that the genetic defect in the majority of sporadic and isolated melorheostosis remains unknown."

The negative LEMD3 result, germline and somatic, in sporadic isolated melorheostosis - written before MAP2K1 was found, and the reason the field went looking.

12q14 Microdeletion Syndrome

Overlapping Features A contiguous-gene deletion spanning LEMD3 and its neighbours (including HMGA2), producing osteopoikilosis together with primordial short stature and developmental delay. Suspect it when a patient with osteopoikilosis also has growth failure or cognitive impairment, and investigate with chromosomal microarray rather than LEMD3 sequencing alone.

Distinguishing Features

Proportionate short stature and developmental delay accompanying the bone findings
Deletion detectable on chromosomal microarray, not on LEMD3 sequencing
Connective tissue nevi not a consistent feature

Show evidence (2 references)

PMID:19277063 SUPPORT Human Clinical

"In their studies on the molecular basis of osteopoikilosis, Menten et al have identified three individuals with microdeletions on chromosome 12q14.4, which removed several genes including LEMD3, the osteopoikilosis gene. In addition to osteopoikilosis, affected individuals had growth retardation..."

Establishes the contiguous-deletion entity in which osteopoikilosis arrives with growth retardation and developmental delay, which is why those features should prompt an array rather than being attributed to Buschke-Ollendorff syndrome.

PMID:19277063 SUPPORT Human Clinical

"The 12q14 deletion did not include LEMD3, and no signs of osteopoikilosis were observed on skeletal radiographs."

Shows the deletion boundary determines whether osteopoikilosis is present, confirming that the skeletal component tracks LEMD3 while the growth and developmental features track neighbouring genes.

🐁

Animal Models

3

Lemd3+/GT heterozygous gene-trap mouse Genetically engineered

A BayGenomics gene-trap allele, studied heterozygously as the direct genetic counterpart of human LEMD3 haploinsufficiency. Assessed by high-resolution micro-CT with full 3D cortical and trabecular histomorphometry, plain radiography read by a trained radiologist, and conventional histology. The result was negative on every measure. This is a substantive negative finding, not a failed experiment: the same allelic state that reliably produces osteopoikilosis in humans produces no skeletal lesion in the mouse, so the species is not dosage-equivalent at this locus and there is at present no animal model of the human bone phenotype.

Species

Mouse

Genotype

Lemd3 heterozygous gene-trap (Lemd3+/GT)

Genes

Lemd3 hgnc:28887

Publication

PMID:19862465

Pathograph links

Focal Trabecular Osteosclerotic Nodule Formation fails to recapitulate fidelity: low observes: tissue Heterozygous Lemd3 gene-trap mice form no osteopoikilosis-like sclerotic nodules on radiography, micro-CT or histology.

Limitations: The mouse does not reproduce the phenotype the model was built to study, so it cannot be used to test therapeutic or mechanistic hypotheses about the human lesion. It remains informative only as evidence that murine skeletal tissue tolerates a halved Lemd3 dose that humans do not. The study examined heterozygotes only, at the ages reported, and did not test whether an aged or challenged animal might eventually develop foci.

Divergences from the human mechanism

species mismatch invalidating

Mouse skeletal tissue appears insensitive to the 50% reduction in Lemd3 dose that produces focal osteosclerosis in humans. The failure is at the level of the organism's response to the genotype, not of the genotype itself: the allele is the correct one.

boundary omission qualifying

The cutaneous arm of the syndrome - dermal connective tissue nevi - was not assessed at all in this study, so the model is silent on the skin phenotype rather than negative for it.

Readouts

Cortical and trabecular bone histomorphometry by micro-CT

Interpretation: Percent bone volume, bone surface/volume ratio, trabecular thickness, separation, number, pattern factor, structure model index and fractal dimension were all statistically indistinguishable from wild type. Direction is left unset because the measurement showed no change in either direction.

Show evidence (1 reference)

PMID:19862465 SUPPORT Model Organism

"No significant differences were found after a t-test statistical analysis."

Reports the negative quantitative micro-CT result for this readout.

Radiographic and histological survey for osteopoikilotic lesions

Interpretation: Neither radiography read by a trained radiologist nor conventional histology identified lesions typical of osteopoikilosis.

Show evidence (1 reference)

PMID:19862465 SUPPORT Model Organism

"X-ray images were evaluated by a trained radiologist, but no typical osteopoikilosis lesions could be recognized."

The radiographic arm of the negative result.

Show evidence (1 reference)

PMID:19862465 SUPPORT Model Organism

"We conclude that the heterozygous Lemd3 gene-trapped mouse is not a good model to study osteopoikilosis and the Buschke-Ollendorff syndrome."

The authors' own conclusion, which is the FAILS_TO_RECAPITULATE claim this link records.

Show evidence (1 reference)

PMID:19862465 SUPPORT Model Organism

"Also, histological analysis did not reveal lesions typical for osteopoikilosis."

The histological arm of the negative result, supporting the model entry as a whole.

Man1 Smad-interacting-domain homozygous deletion mouse Genetically engineered

Embryos lacking the MAN1 Smad-interacting domain, used to show what unopposed Smad2/3 signalling does in vivo. They die at midgestation from a failure of vascular remodelling: the primary capillary plexus forms but is not remodelled, mural cell recruitment fails, Tgfb1 expression rises and Smad2/3 signalling is abnormally activated, with increased extracellular matrix deposition. The tissue is vascular rather than dermal or skeletal and the genotype is homozygous rather than heterozygous, so this is evidence about the pathway, not about the human disease.

Species

Mouse

Genotype

Man1 (Lemd3) homozygous deletion of the Smad-interacting domain

Genes

Lemd3 hgnc:28887

Publication

PMID:16943282

Pathograph links

Increased TGF-beta-SMAD2/3 Transcriptional Output partially recapitulates fidelity: moderate observes: molecular Loss of the Smad-interacting domain activates Smad2/3 signalling in vivo and increases extracellular matrix deposition, which is the molecular claim this pathophysiology node makes.

Limitations: Homozygous rather than the heterozygous state that causes human disease, and embryonic-lethal, so it says nothing about the postnatal, focal, tissue-restricted lesions of BOS. The phenotype observed is vascular; neither bone nor dermis was examined.

Divergences from the human mechanism

boundary omission qualifying

Bone and dermis, the two tissues in which the human lesion appears, are outside the model's boundary; only the embryonic vasculature was studied.

temporal scope qualifying

The animal dies at midgestation, so the model covers only embryogenesis, while osteopoikilotic foci and connective tissue nevi accumulate postnatally over years.

Show evidence (1 reference)

PMID:16943282 SUPPORT Model Organism

"Man1-deficient embryos die at midgestation because of defects in embryonic vasculature; the primary capillary plexus forms, but subsequent remodeling is perturbed."

Establishes what the model actually shows, and the lethality that bounds what it can be used for.

Show evidence (1 reference)

PMID:16943282 SUPPORT Model Organism

"Here, we show that Man1 regulates vascular remodeling by analyzing Man1-deficient embryos lacking the Smad interacting domain."

Defines the allele - deletion of the Smad-interacting domain specifically - which is what makes this animal informative about the SMAD-antagonism arm of the human mechanism rather than about MAN1 in general.

XMAN1 gain- and loss-of-function Xenopus embryo Genetically engineered

The developmental system in which MAN1's BMP-antagonising function was first demonstrated. Overexpressed XMAN1 blocks BMP target genes and suppresses a BMP-responsive promoter; morpholino knockdown of endogenous XMAN1 reduces anterior neuroectoderm. Deletion analysis localises both the neuralising and BMP-antagonising activities to the C-terminal region that binds Smad1, Smad5 and Smad8 - the region human truncating LEMD3 alleles delete.

Species

African clawed frog

Genotype

XMAN1 overexpression and antisense morpholino knockdown in Xenopus laevis embryos

Genes

LEMD3 hgnc:28887

Publication

PMID:12642484

Pathograph links

Loss of Nuclear Envelope R-SMAD Antagonism perturbs fidelity: moderate observes: molecular Bidirectional manipulation of MAN1 dose in a whole embryo, reading out BMP target gene expression, which is the mechanism this node asserts is lost in patients.

Limitations: A developmental patterning assay in an amphibian embryo, not a disease model: neither bone nor dermal connective tissue is assayed, and the perturbations are overexpression and near-complete knockdown rather than the 50% reduction seen in patients.

Divergences from the human mechanism

species mismatch qualifying

Xenopus early embryogenesis. The Smad-binding function is conserved, but the tissue context (neuroectoderm patterning) has no counterpart in the human disease.

proxy quantity qualifying

The measured quantity is BMP target-gene expression (Xhox3, Msx1) and a Xvent2 reporter, standing in for the human node's quantity, which is the amount of R-SMAD sequestered and dephosphorylated at the inner nuclear membrane.

Show evidence (1 reference)

PMID:12642484 SUPPORT Model Organism

"Interference with endogenous XMAN1 functions with antisense morpholino oligos leads to the reduction of anterior neuroectoderm."

The loss-of-function arm of the manipulation, showing that endogenous MAN1 dose matters in vivo.

Show evidence (1 reference)

PMID:12642484 SUPPORT Model Organism

"Using a Xenopus expression screening approach with an anterior neuroectoderm cDNA library, we have identified an inner nuclear membrane protein, XMAN1, as a novel neuralizing factor that is encoded by the Xenopus ortholog of human MAN1."

Establishes XMAN1 as the Xenopus orthologue of human MAN1, which is what licenses using this system to interrogate the human protein's function.

{ }

Source YAML

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name: Buschke-Ollendorff Syndrome
creation_date: "2026-09-05T00:00:00Z"
description: >-
  Buschke-Ollendorff syndrome (BOS) is a rare autosomal dominant disorder of bone
  and dermal connective tissue caused by heterozygous loss-of-function variants in
  LEMD3, which encodes MAN1, an integral protein of the inner nuclear membrane.
  MAN1 binds receptor-regulated SMADs at the nuclear envelope and terminates BMP
  (SMAD1/5/8) and TGF-beta/activin (SMAD2/3) signalling; haploinsufficiency
  therefore de-represses SMAD-driven transcription. The same lesion produces two
  cardinal manifestations in two tissues. In bone it drives focal modeling-based
  formation of compact lamellar nodules within trabecular bone, seen radiographically
  as osteopoikilosis - multiple small, round, broadly symmetric periarticular
  sclerotic foci that are clinically silent and usually discovered incidentally. In
  skin it drives fibroblast overproduction of elastin and collagen, producing
  connective tissue nevi (elastomas, collagenomas, or mixed lesions, historically
  dermatofibrosis lenticularis disseminata). Expressivity is strikingly variable
  within a single family, so a carrier may show nevi alone, osteopoikilosis alone,
  or both. Segmental cortical hyperostosis resembling melorheostosis occurs in a
  minority of LEMD3 kindreds, but sporadic isolated melorheostosis is a genetically
  distinct condition driven by somatic MAP2K1 mutation and is not part of BOS. The
  main clinical value of recognising BOS is avoiding misdiagnosis of the sclerotic
  bone foci as osteoblastic metastases.
category: Mendelian
parents:
- Musculoskeletal Disease
- Skin Disease
- Genetic Disease
disease_term:
  preferred_term: Buschke-Ollendorff syndrome
  term:
    id: MONDO:0008157
    label: Buschke-Ollendorff syndrome
synonyms:
- dermatofibrosis lenticularis disseminata with osteopoikilosis
- disseminated dermatofibrosis with osteopoikilosis
- dermatoosteopoikilosis
- osteopathia condensans disseminata
- osteopoikilosis with connective tissue nevi
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
  - classification_value: DERMATOLOGY
  mechanistic_category:
  - classification_value: laminopathy
    notes: >-
      LEMD3/MAN1 is an integral protein of the inner nuclear membrane rather than a
      lamin itself, but MONDO classifies Buschke-Ollendorff syndrome under
      MONDO:0021106 laminopathy on the strength of the nuclear-envelope lesion, and
      the disorder is discussed with the nuclear envelopathies in the laminopathy
      literature.
  isds_skeletal_category:
  - classification_value: osteosclerotic_disorders
    notes: >-
      ISDS Nosology and Classification of Genetic Skeletal Disorders, 2023 revision
      (Unger et al., PMID:36779427), group 25 "Osteosclerotic disorders", which
      covers non-osteopetrotic increased bone mass and lists osteopoikilosis and
      melorheostosis (LEMD3, MAP2K1). Assigned by the enum key rather than the group
      number, which is not stable across revisions.
inheritance:
- name: Autosomal Dominant
  description: >-
    A single heterozygous loss-of-function LEMD3 allele is sufficient. Transmission
    is vertical, family history is the rule, and each child of an affected person has
    a 50% risk of inheriting the variant. Penetrance of the *syndrome* is hard to
    call complete because the two components are ascertained differently: a carrier
    with radiographically silent skin and no reason for an x-ray may look unaffected.
    Expressivity within a family is emphatically variable - relatives carrying the
    identical variant may have nevi alone, osteopoikilosis alone, or both - and no
    genotype-phenotype correlation has been established.
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: INCOMPLETE
  expressivity: VARIABLE
  evidence:
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autosomal dominant OPK and BOS feature widespread foci of osteosclerotic trabeculae without or with skin lesions, respectively."
    explanation: States the autosomal dominant inheritance of both osteopoikilosis and Buschke-Ollendorff syndrome.
  - reference: PMID:19438932
    reference_title: "Novel and recurrent germline LEMD3 mutations causing Buschke-Ollendorff syndrome and osteopoikilosis but not isolated melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our results further expand the LEMD3 mutation repertoire, corroborate the extreme interfamilial and intrafamilial clinical variability of LEMD3 mutations, and underline the lack of a clear phenotype-genotype correlation in BOS."
    explanation: Directly supports variable expressivity within and between families and the absence of a genotype-phenotype correlation.
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, the fathers of probands 2 and 6 and the mother of proband 1, who all carry the same mutation as their offspring, did not present with BOS-related skin lesions upon physical examination."
    explanation: >-
      Three obligate carriers in this series carried the proband's LEMD3 variant with
      no cutaneous manifestation, which is the clearest available demonstration that
      the skin component is not fully penetrant within a family.
prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: BAND_1_9_PER_100000
  rate_per_100000: 5.0
  notes: >-
    The frequently repeated figure is approximately 1 in 20,000, i.e. 5 per 100,000.
    It is recorded here as measure_type UNKNOWN rather than as an incidence or a point
    prevalence: the source states it as an "estimated incidence" but supplies neither a
    denominator population nor an observation period, and it traces back through the
    case-series literature rather than to a registry. Ascertainment is certainly
    incomplete in both directions - osteopoikilosis is asymptomatic and found
    incidentally, and the cutaneous nevi are easily dismissed as unremarkable papules -
    so the true figure could lie either side. No population-based BOS prevalence study
    was identified.
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "initially described by Buschke and Ollendorff in 1928, is a rare autosomal dominant genetic disease with an estimated incidence of 1 in 20,000"
    explanation: >-
      Source of the 1-in-20,000 figure. The paper cites it to earlier literature rather
      than deriving it, which is why the measure type is left UNKNOWN here.
- population: Published Buschke-Ollendorff syndrome case reports (systematic review of 164 cases)
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    A 2016 systematic review recovered 164 reported cases from 48 publications with no
    date or language restriction, which bounds the size of the published literature
    rather than the size of the affected population.
  evidence:
  - reference: PMID:26708699
    reference_title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In total, 594 reports were discovered, of which 546 (92%) were excluded. The remaining 48 accounted for 164 cases."
    explanation: Quantifies the entire published case literature for this disorder as of 2016.
has_subtypes:
- name: Complete BOS
  display_name: Complete Buschke-Ollendorff syndrome (nevi plus osteopoikilosis)
  description: >-
    The full syndromic presentation: connective tissue nevi together with radiographic
    osteopoikilosis in the same individual. This was just over half of the cases in the
    2016 systematic review.
  evidence:
  - reference: PMID:26708699
    reference_title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Skin lesions were noted in 24% of cases and bony lesions in 20%, while 54% of patients had both."
    explanation: >-
      Partitions reported BOS cases into skin-only, bone-only, and complete forms, and
      is the quantitative basis for treating the three as recognised presentations of
      one allelic disorder rather than as distinct diseases.
- name: Skin-Limited BOS
  display_name: Skin-limited Buschke-Ollendorff syndrome (connective tissue nevi without osteopoikilosis)
  description: >-
    Connective tissue nevi in a member of an LEMD3 kindred with no osteopoikilosis on
    radiographs. Some of this is genuine tissue-restricted expression and some is
    age-related: osteopoikilotic foci may not be radiographically apparent in early
    childhood, so a negative film in a young child does not settle the question.
  evidence:
  - reference: PMID:11298556
    reference_title: "The Buschke-Ollendorff syndrome presenting as familial elastic tissue naevi."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We present a family with Buschke-Ollendorff syndrome presenting as elastic tissue naevi without evidence of osteopoikilosis."
    explanation: A whole family expressing the cutaneous component with no radiographic bone component.
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Proband 3 and proband 5 had an X-ray examination of pelvis but did not exhibit any signs of OPK."
    explanation: Two LEMD3-variant probands with cutaneous disease and negative pelvic radiographs.
- name: Bone-Limited BOS
  display_name: Bone-limited expression (isolated osteopoikilosis in an LEMD3 kindred)
  subtype_term:
    preferred_term: isolated osteopoikilosis
    term:
      id: MONDO:0015634
      label: isolated osteopoikilosis
  description: >-
    Radiographic osteopoikilosis with no connective tissue nevus, in a carrier of the
    family's LEMD3 variant. This is the same allelic disorder expressed in one tissue
    only, and it is how most silent carriers come to attention. The MONDO binding names
    the concept accurately but is a cross-reference rather than a claim that BOS
    subsumes sporadic isolated osteopoikilosis as an independent entity: MONDO places
    MONDO:0015634 under osteopoikilosis, not under Buschke-Ollendorff syndrome.
  genes:
  - preferred_term: LEMD3
    term:
      id: hgnc:28887
      label: LEMD3
  evidence:
  - reference: PMID:16470551
    reference_title: "Germline LEMD3 mutations are rare in sporadic patients with isolated melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We confirm that loss-of-function mutations in the LEMD3 gene can result in either osteopoikilosis or BOS."
    explanation: >-
      States that the same class of LEMD3 loss-of-function allele produces either the
      bone-only phenotype or the full syndrome, which is what makes bone-limited
      expression a subtype rather than a separate disease.
- name: BOS with Melorheostosis
  display_name: Buschke-Ollendorff syndrome with melorheostosis-like segmental hyperostosis
  subtype_term:
    preferred_term: melorheostosis with osteopoikilosis
    term:
      id: MONDO:0015995
      label: melorheostosis with osteopoikilosis
  description: >-
    A minority of LEMD3 kindreds contain an individual with a large asymmetric area of
    dense cortical bone read as melorheostosis, superimposed on the symmetric
    osteopoikilotic foci. What converts one segment is unknown: no somatic second hit
    in LEMD3 has ever been demonstrated in such lesions. Distinguish this from sporadic
    isolated melorheostosis, which is a different disease - see the discussion entry
    "melorheostosis_attribution".
  evidence:
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In some OPK and BOS families, an individual may have relatively large, asymmetric areas of dense cortical bone interpreted as melorheostosis (MEL)."
    explanation: Describes melorheostosis-like segmental hyperostosis as an occasional within-family manifestation of OPK/BOS.
  - reference: PMID:17622481
    reference_title: "A novel LEMD3 mutation common to patients with osteopoikilosis with and without melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The LEMD3 mutation reported was clearly the cause of osteopoikilosis in the two families but its relationship to melorheostosis in one of the family members is still unclear."
    explanation: >-
      One family, one LEMD3 allele, and melorheostosis in only one member - the
      cleanest statement that the LEMD3 genotype alone does not determine the
      segmental lesion.
pathophysiology:
- name: LEMD3 Haploinsufficiency
  description: >-
    A heterozygous germline loss-of-function variant in LEMD3 - nonsense, frameshift,
    splice-disrupting, or whole-gene deletion - halves the functional dose of MAN1, a
    roughly 100-kDa integral protein of the inner nuclear membrane. Truncating alleles
    remove the C-terminal nucleoplasmic region that carries the SMAD-interacting
    module, so the residual protein cannot perform the function the wild-type allele
    is losing. No obligate somatic second hit has been found in lesional tissue, so
    the disorder is modelled as true haploinsufficiency rather than as a two-hit
    mosaic condition.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  genes:
  - preferred_term: LEMD3
    term:
      id: hgnc:28887
      label: LEMD3
  cellular_components:
  - preferred_term: inner nuclear membrane
    term:
      id: GO:0005637
      label: nuclear inner membrane
  genetic_context:
    gene:
      preferred_term: LEMD3
      term:
        id: hgnc:28887
        label: LEMD3
    zygosity: HETEROZYGOUS
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      Heterozygous germline truncating and deletion alleles across the LEMD3 coding
      sequence; reported examples include p.Y441X, p.L478X, p.R655X, p.W621X and
      p.Y871X, plus the frameshift c.332_333insTC.
  downstream:
  - target: Loss of Nuclear Envelope R-SMAD Antagonism
    causal_link_type: DIRECT
    description: >-
      Reduced MAN1 dose at the inner nuclear membrane means fewer binding sites for
      receptor-activated SMADs, so less of the pathway-terminating activity MAN1
      provides.
    evidence:
    - reference: PMID:15489854
      reference_title: "Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "In this study, LEMD3 interacted with BMP and activin-TGFbeta receptor-activated Smads and antagonized both signaling pathways in human cells."
      explanation: >-
        Establishes in human cells that the protein lost by haploinsufficiency is the
        one that antagonises R-SMAD signalling, which is the step this edge asserts.
  evidence:
  - reference: PMID:15489854
    reference_title: "Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All the affected individuals that we investigated were heterozygous with respect to a loss-of-function mutation in LEMD3 (also called MAN1), which encodes an inner nuclear membrane protein."
    explanation: The gene-discovery study identifying heterozygous LEMD3 loss of function as the lesion, and MAN1 as an inner nuclear membrane protein.
  - reference: PMID:15489854
    reference_title: "Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A somatic mutation in the second allele of LEMD3 could not be identified in fibroblasts from affected skin of an individual with BOS and an individual with melorheostosis."
    explanation: >-
      Negative search for a somatic second hit in lesional fibroblasts, which is why
      this node is modelled as haploinsufficiency rather than biallelic inactivation.
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the two BOS families, a heterozygous nonsense mutation (exon 1, c.1323C>A, p.Y441X) and a heterozygous frame-shift mutation (exon 1, c.332_333insTC) were identified."
    explanation: Two independent BOS families with heterozygous truncating LEMD3 alleles, illustrating the variant classes involved.
- name: Loss of Nuclear Envelope R-SMAD Antagonism
  description: >-
    MAN1's C-terminal nucleoplasmic region binds the MAD homology 2 (MH2) domain of
    receptor-regulated SMADs at the inner nuclear membrane, in a ligand-independent
    manner and without binding the common mediator SMAD4. The interaction sequesters
    R-SMADs at the nuclear periphery and facilitates their dephosphorylation, so that
    the pathway is terminated rather than merely attenuated. Losing half of this
    capacity removes a brake, not a signal: nothing upstream of the receptor is
    altered, and the defect is in how quickly an activated SMAD is switched off.
    Recent work adds that the LEMD3-SMAD2/3 interaction is mechanosensitive, weakening
    as extracellular matrix stiffness rises, which offers one route by which a
    uniformly halved gene dose could produce focal rather than uniform lesions.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  molecular_functions:
  - preferred_term: R-SMAD binding
    term:
      id: GO:0070412
      label: R-SMAD binding
  biological_processes:
  - preferred_term: negative regulation of BMP signaling pathway
    modifier: DECREASED
    term:
      id: GO:0030514
      label: negative regulation of BMP signaling pathway
  - preferred_term: negative regulation of TGF-beta receptor signaling pathway
    modifier: DECREASED
    term:
      id: GO:0030512
      label: negative regulation of transforming growth factor beta receptor signaling pathway
  - preferred_term: SMAD protein signal transduction
    term:
      id: GO:0060395
      label: SMAD protein signal transduction
  cellular_components:
  - preferred_term: inner nuclear membrane
    term:
      id: GO:0005637
      label: nuclear inner membrane
  downstream:
  - target: Increased BMP-SMAD1/5/8 Transcriptional Output
    causal_link_type: DIRECT
    description: >-
      MAN1 binds SMAD1, SMAD5 and SMAD8; removing that binding leaves BMP-activated
      R-SMADs phosphorylated and transcriptionally competent for longer.
    evidence:
    - reference: PMID:12642484
      reference_title: "XMAN1, an inner nuclear membrane protein, antagonizes BMP signaling by interacting with Smad1 in Xenopus embryos."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Deletion mutant analyses reveal that the neuralizing and BMP-antagonizing activities of XMAN1 reside in the C-terminal region, and that the C-terminal region binds to Smad1, Smad5 and Smad8, which are intracellular mediators of the BMP pathway."
      explanation: >-
        Maps the BMP-antagonising activity of the MAN1 orthologue to the same
        C-terminal region that binds the BMP R-SMADs - the region truncating LEMD3
        alleles delete - so losing it releases BMP-SMAD signalling.
  - target: Increased TGF-beta-SMAD2/3 Transcriptional Output
    causal_link_type: DIRECT
    description: >-
      The same C-terminal module binds SMAD2 and SMAD3, so MAN1 loss equally releases
      the TGF-beta and activin arm.
    evidence:
    - reference: PMID:15647271
      reference_title: "The integral inner nuclear membrane protein MAN1 physically interacts with the R-Smad proteins to repress signaling by the transforming growth factor-beta superfamily of cytokines."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Overexpression of MAN1 results in inhibition of R-Smad phosphorylation, heterodimerization with Smad4 and nuclear translocation, and repression of transcriptional activation of the TGFbeta, BMP2, and activin-responsive promoters."
      explanation: >-
        Gain-of-MAN1 suppresses TGF-beta-, BMP- and activin-responsive transcription;
        loss of MAN1 is the inverse manipulation, so this supports the direction of
        the edge through an inverted experiment.
      directness: INDIRECT
  evidence:
  - reference: PMID:15647271
    reference_title: "The integral inner nuclear membrane protein MAN1 physically interacts with the R-Smad proteins to repress signaling by the transforming growth factor-beta superfamily of cytokines."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "MAN1, through the RNA recognition motif, associates with R-Smads but not Smad4 at the inner nuclear membrane in a ligand-independent manner."
    explanation: Defines the physical interaction - R-SMADs but not SMAD4, at the inner nuclear membrane - that this node says is lost.
  - reference: PMID:30321401
    reference_title: "Structural basis for receptor-regulated SMAD recognition by MAN1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "MAN1 interacts with MAD homology 2 (MH2) domains of R-SMAD proteins using its C-terminal U2AF homology motif (UHM) domain and UHM ligand motif (ULM) and facilitates R-SMAD dephosphorylation."
    explanation: >-
      Structural account of the interaction and of the terminating step -
      dephosphorylation of the R-SMAD - that MAN1 facilitates.
  - reference: PMID:30108174
    reference_title: "LEM domain-containing protein 3 antagonizes TGFβ-SMAD2/3 signaling in a stiffness-dependent manner in both the nucleus and cytosol."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We confirmed that a consensus C-terminal LEMD3 fragment binds SMAD2/3 in a stiffness-dependent manner throughout the cell and is sufficient for antagonizing SMAD2/3 signaling."
    explanation: >-
      Shows the antagonism is modulated by matrix stiffness, the observation behind the
      note in this node's description that a uniform gene-dose defect might still act
      focally.
- name: Increased BMP-SMAD1/5/8 Transcriptional Output
  description: >-
    With MAN1 antagonism halved, BMP receptor activation yields more, and more
    prolonged, SMAD1/5/8-driven transcription. BMP signalling is the principal
    osteogenic input to the osteoblast lineage, so this is the arm that carries the
    skeletal phenotype. The direct measurement in human BOS tissue is still missing:
    the pathway effect is established in cell systems and in orthologue models, and its
    operation in patient osteoblasts is inferred.
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  biological_processes:
  - preferred_term: BMP signaling pathway
    modifier: INCREASED
    term:
      id: GO:0030509
      label: BMP signaling pathway
  - preferred_term: positive regulation of ossification
    modifier: INCREASED
    term:
      id: GO:0045778
      label: positive regulation of ossification
  downstream:
  - target: Bone Lining Cell Activation and Modeling-Based Bone Formation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Excess BMP-SMAD output in the osteoblast lineage is the proposed driver of the
      focal osteogenic response. The intermediate steps between a halved MAN1 dose and
      the recruitment of a particular patch of bone lining cells are not known, which
      is why the link type is INDIRECT_UNKNOWN_INTERMEDIATES rather than DIRECT.
    evidence:
    - reference: PMID:32151766
      reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "These observations indicate that LEMD3 may be important for the activation of bone lining cells leading to modeling-based bone formation."
      explanation: >-
        The authors connect LEMD3 function to bone lining cell activation, which is the
        step this edge asserts. They do not measure BMP-SMAD output itself, so the edge
        remains inferential on the signalling side.
      directness: INDIRECT
  evidence:
  - reference: PMID:15489854
    reference_title: "Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Osteopoikilosis, Buschke-Ollendorff syndrome (BOS) and melorheostosis are disorders characterized by increased bone density."
    explanation: >-
      Frames the shared consequence of the LEMD3 lesion as increased bone density,
      the organism-level readout of this signalling arm.
  - reference: PMID:12642484
    reference_title: "XMAN1, an inner nuclear membrane protein, antagonizes BMP signaling by interacting with Smad1 in Xenopus embryos."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Importantly, XMAN1 antagonizes bone morphogenetic protein (BMP) signaling downstream of its receptor Alk3, as judged by animal cap assays, in which XMAN1 blocks expression of downstream targets of BMP signaling (Xhox3 and Msx1), and by luciferase reporter assays, in which XMAN1 suppresses BMP-dependent activation of the Xvent2 promoter."
    explanation: >-
      Demonstrates in vivo that MAN1 restrains BMP target-gene expression downstream of
      the receptor; its loss therefore raises BMP transcriptional output.
    directness: INDIRECT
- name: Increased TGF-beta-SMAD2/3 Transcriptional Output
  description: >-
    The TGF-beta and activin arm is released in parallel. In dermal fibroblasts,
    TGF-beta is the dominant transcriptional stimulus for tropoelastin and fibrillar
    collagen, so this arm carries the cutaneous phenotype. The clearest human evidence
    is functional rather than transcriptional: fibroblasts cultured from BOS skin
    produce several-fold excess tropoelastin and carry elevated elastin mRNA, exactly
    the profile expected from unopposed TGF-beta drive.
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  biological_processes:
  - preferred_term: transforming growth factor beta receptor signaling pathway
    modifier: INCREASED
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
  - preferred_term: extracellular matrix organization
    modifier: DYSREGULATED
    term:
      id: GO:0030198
      label: extracellular matrix organization
  downstream:
  - target: Dermal Fibroblast Elastin and Collagen Overproduction
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      TGF-beta1 is an established transcriptional inducer of tropoelastin in dermal
      fibroblasts, so unopposed SMAD2/3 output raises elastin and collagen synthesis.
    evidence:
    - reference: PMID:1629625
      reference_title: "Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Transforming growth factor-beta 1 (TGF beta 1), a powerful stimulus for elastin production, brought about similar relative increases in normal and BOS strains."
      explanation: >-
        Identifies TGF-beta1 as the stimulus that drives elastin production in these
        fibroblasts, which is the intermediate this edge relies on. Note the same paper
        found BOS strains still respond normally to exogenous TGF-beta1, so the defect
        looks like a raised basal set-point rather than receptor hypersensitivity.
  - target: Bone Lining Cell Activation and Modeling-Based Bone Formation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      TGF-beta acts on the osteoblast lineage as well, so the skeletal lesion is not
      attributed to the BMP arm alone. The relative contribution of the two arms to the
      bone phenotype has not been separated in human tissue.
  evidence:
  - reference: PMID:16943282
    reference_title: "Man1, an inner nuclear membrane protein, regulates vascular remodeling by modulating transforming growth factor beta signaling."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We have demonstrated, in Man1-deficient embryos, the expression of Tgfb1 is upregulated and Smad2/3 signaling is abnormally activated, resulting in increased extracellular matrix deposition, a hallmark of the resolution phase of angiogenesis."
    explanation: >-
      In vivo confirmation that losing MAN1's Smad-interacting domain activates Smad2/3
      signalling and increases extracellular matrix deposition - the two claims this
      node makes - although in a homozygous mouse and in vascular rather than dermal
      tissue.
    directness: INDIRECT
  - reference: PMID:30108174
    reference_title: "LEM domain-containing protein 3 antagonizes TGFβ-SMAD2/3 signaling in a stiffness-dependent manner in both the nucleus and cytosol."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We showed that LEMD3-SMAD2/3 interactions are inversely correlated with ECM stiffness and TGFβ-driven luciferase activity and that LEMD3 expression is correlated with the mechanical response of the TGFβ-driven luciferase reporter."
    explanation: Ties LEMD3 level directly to the magnitude of TGF-beta-driven transcriptional output in human fibroblasts.
- name: Bone Lining Cell Activation and Modeling-Based Bone Formation
  description: >-
    Human bone biopsies from two women with LEMD3 variants show what the skeletal
    lesion actually is at the tissue level, and it is not accelerated remodelling.
    Overall bone turnover markers and remodelling rate were normal; instead, discrete
    areas of trabecular bone had been replaced by compact lamellar bone laid down by
    modeling-based formation - apposition on a quiescent surface, without a preceding
    resorption cavity - which implicates activation of bone lining cells. Woven bone
    was absent, so this is orderly lamellar deposition rather than a reactive or
    repair response.
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: bone lining cell
    term:
      id: CL:0000062
      label: osteoblast
  - preferred_term: osteocyte
    term:
      id: CL:0000137
      label: osteocyte
  biological_processes:
  - preferred_term: ossification
    modifier: INCREASED
    term:
      id: GO:0001503
      label: ossification
  - preferred_term: bone mineralization
    term:
      id: GO:0030282
      label: bone mineralization
  locations:
  - preferred_term: trabecular bone tissue
    term:
      id: UBERON:0002483
      label: trabecular bone tissue
  downstream:
  - target: Focal Trabecular Osteosclerotic Nodule Formation
    causal_link_type: DIRECT
    description: >-
      Modeling-based apposition within the marrow cavity and on the endocortex builds
      the discrete sclerotic noduli.
    evidence:
    - reference: PMID:32151766
      reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Histomorphometric analyses of the sclerotic lesions revealed compact lamellar bone with a normal bone remodeling rate, but partly replaced by modeling-based bone formation."
      explanation: Directly attributes the sclerotic nodules to modeling-based formation rather than to altered remodelling.
  - target: Segmental Cortical Hyperostosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      In the minority of LEMD3 kindreds that show melorheostosis-like disease, the same
      osteogenic drive appears to act over a much larger, asymmetric cortical segment.
      What restricts and amplifies it there is unknown; see the "melorheostosis_attribution"
      discussion entry.
  evidence:
  - reference: PMID:32151766
    reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These observations indicate that LEMD3 may be important for the activation of bone lining cells leading to modeling-based bone formation."
    explanation: The authors' own mechanistic reading of their histomorphometry, and the basis for naming this node after bone lining cell activation.
  - reference: PMID:32151766
    reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bone turnover markers were within normal range."
    explanation: >-
      Excludes a generalised high-turnover state, which is why the node is framed as
      focal modeling rather than as systemic osteogenic overactivity.
- name: Focal Trabecular Osteosclerotic Nodule Formation
  description: >-
    The end-organ lesion of the bone arm: discrete, stellate to round nodules of
    compact lamellar bone, a few millimetres across, sitting within the trabecular
    cavity and on the endocortex, concentrated in epiphyses and metaphyses of long
    bones and in the pelvis, carpus and tarsus. They are metabolically quiet, do not
    remodel abnormally, and do not compromise the bone. Their broadly symmetric
    distribution is what distinguishes them radiographically from metastatic deposits.
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  locations:
  - preferred_term: trabecular bone tissue
    term:
      id: UBERON:0002483
      label: trabecular bone tissue
  - preferred_term: bone element
    term:
      id: UBERON:0001474
      label: bone element
  downstream:
  - target: Osteopoikilosis
    causal_link_type: DIRECT
    description: The nodules are the radiographic finding called osteopoikilosis.
    evidence:
    - reference: PMID:17087626
      reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "OPK is an autosomal dominant, usually benign, skeletal dysplasia featuring multiple, small, especially metaphyseal, oval or round, dense trabecular foci distributed symmetrically throughout the skeleton."
      explanation: Maps the dense trabecular foci onto the clinical-radiographic entity osteopoikilosis.
  - target: Increased Bone Mineral Density
    causal_link_type: DIRECT
    description: >-
      Compact lamellar nodules are denser than the trabecular bone they replace, which
      is what raises regional bone mineral density.
    evidence:
    - reference: PMID:32151766
      reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "aBMD Z-scores were comparable to that of controls in the lumbar spine and increased at the hip."
      explanation: >-
        Measures the densitometric consequence, and simultaneously bounds it - the
        increase is regional, not generalised.
  evidence:
  - reference: PMID:32151766
    reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Woven bone was not observed in the nodules."
    explanation: >-
      Establishes that the nodules are lamellar, not woven, which excludes a reactive
      or repair-type ossification and is a specific structural claim about this node.
  - reference: PMID:26694706
    reference_title: "Identification of a novel LEMD3 Y871X mutation in a three-generation family with osteopoikilosis and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Osteopoikilosis is a rare and benign autosomal dominant genetic disorder, characterized by a symmetric but unequal distribution of multiple hyperostotic areas in different parts of the skeleton."
    explanation: Describes the symmetric but unequal skeletal distribution of the foci that this node produces.
- name: Segmental Cortical Hyperostosis
  description: >-
    A large, asymmetric, sharply demarcated region of dense cortical bone confined to
    one limb segment, radiographically the "flowing hyperostosis" or dripping-candle-wax
    pattern of melorheostosis. It occurs in a minority of LEMD3 kindreds, superimposed
    on osteopoikilosis. Unlike the osteopoikilotic nodules it can be symptomatic, with
    pain, deformity and joint restriction. This node deliberately makes no claim about
    the *sporadic* melorheostosis seen without osteopoikilosis, which is a different
    disease with a different mechanism.
  biological_scale: TISSUE
  mechanism_confidence: HYPOTHETICAL
  locations:
  - preferred_term: bone element
    term:
      id: UBERON:0001474
      label: bone element
  downstream:
  - target: Melorheostosis
    causal_link_type: DIRECT
    description: The segmental cortical lesion is what is read on the radiograph as melorheostosis.
    evidence:
    - reference: PMID:30138550
      reference_title: "Distinct Clinical and Pathological Features of Melorheostosis Associated With Somatic MAP2K1 Mutations."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The common feature of all these patterns is the radiographic and histologic appearance of excess cortical bone in an asymmetrical focal pattern."
      explanation: >-
        States what the several aetiologically distinct melorheostosis patterns share -
        asymmetric focal excess cortical bone - which is the tissue lesion this edge
        maps onto the radiographic phenotype.
  evidence:
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'MEL, however, classically refers to a sporadic, troublesome skeletal dysostosis featuring large, asymmetric, "flowing hyperostosis" of long bone cortices often with overlying, constricting soft tissue abnormalities.'
    explanation: Defines the radiographic and clinical character of the segmental cortical lesion modelled by this node.
  - reference: PMID:30138550
    reference_title: "Distinct Clinical and Pathological Features of Melorheostosis Associated With Somatic MAP2K1 Mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A second subset of patients with germline mutations in LEMD3 and radiographic appearance of melorheostosis with coexisting familial osteopoikilosis has been described."
    explanation: >-
      Establishes the LEMD3-associated, osteopoikilosis-accompanied form of
      melorheostosis as a recognised second subset, separate from the sporadic
      MAP2K1-driven form.
- name: Dermal Fibroblast Elastin and Collagen Overproduction
  description: >-
    Fibroblasts cultured from BOS skin produce two- to eight-fold more tropoelastin
    than normal dermal fibroblasts, and carry correspondingly elevated elastin mRNA -
    so the defect sits at or above the level of steady-state transcript abundance
    rather than in post-translational assembly. Notably the excess is not confined to
    clinically involved skin: apparently uninvolved skin from the same patient was
    elevated more than three-fold, which argues that the cellular defect is
    constitutive across the dermis and that something else localises the visible
    lesions. Collagen synthesis is altered in parallel, giving the collagen-rich
    lesions their character.
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: dermal fibroblast
    term:
      id: CL:0002551
      label: fibroblast of dermis
  biological_processes:
  - preferred_term: elastic fiber assembly
    modifier: INCREASED
    term:
      id: GO:0048251
      label: elastic fiber assembly
  - preferred_term: collagen fibril organization
    modifier: ABNORMAL
    term:
      id: GO:0030199
      label: collagen fibril organization
  locations:
  - preferred_term: dermis
    term:
      id: UBERON:0002067
      label: dermis
  downstream:
  - target: Dermal Connective Tissue Nevus Formation
    causal_link_type: DIRECT
    description: >-
      Sustained matrix overproduction by dermal fibroblasts accumulates as the
      hamartomatous dermal deposit that is clinically a connective tissue nevus.
    evidence:
    - reference: PMID:1629625
      reference_title: "Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Elastin mRNA levels were elevated in all patient strains, suggesting that Buschke-Ollendorff syndrome may result, at least in part, from abnormal regulation of extracellular matrix metabolism that leads to increased steady-state levels of elastin mRNA and elastin accumulation in the dermis."
      explanation: >-
        The authors draw exactly this edge - elevated elastin mRNA leading to elastin
        accumulation in the dermis - from their own measurements.
  evidence:
  - reference: PMID:1629625
    reference_title: "Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Cultured fibroblasts from both patients produced 2-8 times more tropoelastin than normal skin fibroblasts in the presence of 10% calf serum."
    explanation: Quantifies the fibroblast overproduction of tropoelastin that defines this node.
  - reference: PMID:1629625
    reference_title: "Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Involved skin fibroblasts of one patient produced up to eight times normal levels, whereas apparently uninvolved skin was also elevated more than threefold."
    explanation: >-
      Supports the statement that the cellular defect extends to clinically normal
      skin, which is the observation behind treating lesion localisation as unexplained.
- name: Dermal Connective Tissue Nevus Formation
  description: >-
    Accumulated matrix forms a hamartomatous dermal nodule. Histology is
    heterogeneous and this is the practically important point: the classic lesion is an
    elastoma, with large, thickened, haphazardly arrayed elastic fibres visible on
    Victoria blue or other elastic stains, but a substantial minority are collagenomas
    of dense hypocellular collagen with normal elastic tissue, some are mixed, and
    increased interstitial dermal mucin is common and easily missed. A biopsy read as
    unremarkable on routine haematoxylin and eosin therefore does not exclude BOS, and
    two lesions from the same patient at different body sites can look different.
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  locations:
  - preferred_term: dermis
    term:
      id: UBERON:0002067
      label: dermis
  - preferred_term: skin of body
    term:
      id: UBERON:0002097
      label: skin of body
  downstream:
  - target: Connective Tissue Nevi
    causal_link_type: DIRECT
    description: The dermal deposit is what presents clinically as a connective tissue nevus.
    evidence:
    - reference: PMID:32206820
      reference_title: "Buschke-Ollendorff syndrome in a 6-year-old patient: clinical and histopathological aspects of a rare disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We present the case of a 6-year-old male patient with yellowish papules that coalesced to form plaques localized on both thighs and on the upper limbs consistent with a connective tissue nevus (CTN) diagnosis."
      explanation: Links the dermal lesion to the clinical diagnosis of connective tissue nevus.
  - target: Collagenoma
    causal_link_type: DIRECT
    description: >-
      Where the accumulated matrix is predominantly collagen, the lesion is classified
      as a collagenoma.
    evidence:
    - reference: PMID:40195882
      reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Masson's trichrome staining indicated collagenoma in probands 3 (foot) and 4 (Fig. S1A)."
      explanation: Demonstrates the collagen-predominant outcome of the same dermal process.
  - target: Increased Number of Elastic Fibers in the Dermis
    causal_link_type: DIRECT
    description: >-
      Where elastic tissue predominates, the deposit presents as thickened, increased
      and disordered dermal elastic fibres - the elastoma pattern.
    evidence:
    - reference: PMID:40195882
      reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Victoria blue staining revealed that the dermis of probands 2, 3 (buttocks), 4, 5, and 6 exhibited large, thickened, and haphazardly arrayed elastic fibres (Fig. S1A)."
      explanation: Demonstrates the elastin-predominant outcome of the same dermal process.
  evidence:
  - reference: PMID:32206820
    reference_title: "Buschke-Ollendorff syndrome in a 6-year-old patient: clinical and histopathological aspects of a rare disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two skin lesion patterns have been described because they may be of either elastic tissue (juvenile elastoma) or collagenous composition (dermatofibrosis lenticularis disseminata)."
    explanation: States the elastoma versus collagenoma division of the dermal lesion that this node describes.
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Notably, biopsies from a plantar foot nodule and a buttock nodule in proband 3 presented differing histological features, suggesting that lesion location may influence pathological presentation, even within the same individual."
    explanation: Supports the claim that histology varies by site within one patient, not only between patients.
phenotypes:
- name: Connective Tissue Nevi
  category: Dermatological
  frequency: FREQUENT
  diagnostic: true
  description: >-
    Non-tender, flesh-coloured to yellowish or reddish papules and nodules, often
    coalescing into cobblestone-like plaques, asymmetrically distributed and favouring
    the trunk, abdomen, buttocks and thighs. Onset is usually congenital, infantile or
    in childhood, though presentations as late as the fifth decade are recorded. In the
    2016 systematic review, 78% of reported cases (24% skin only plus 54% with both)
    had cutaneous lesions; that is a literature frequency, not a penetrance estimate,
    since dermatological journals over-report the skin component.
  phenotype_term:
    preferred_term: Connective tissue nevi
    term:
      id: HP:0100898
      label: Connective tissue nevi
  evidence:
  - reference: PMID:26708699
    reference_title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "BOS commonly presents with nontender connective tissue naevi and sclerotic bony lesions (osteopoikilosis [OPK])."
    explanation: Establishes connective tissue nevi as one of the two cardinal presenting features.
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinically, all 6 probands presented with multiple yellowish to red papules and nodules, some of which coalesced into cobblestone-like nevoid plaques (Fig. 1A)."
    explanation: Describes the morphology and coalescence pattern of the nevi in a genetically confirmed series.
- name: Osteopoikilosis
  category: Skeletal
  frequency: FREQUENT
  diagnostic: true
  description: >-
    Multiple small (roughly 1-10 mm), round to ovoid, well-defined sclerotic foci
    distributed broadly symmetrically in periarticular cancellous bone - epiphyses and
    metaphyses of long bones, pelvis, carpus and tarsus. Asymptomatic, non-progressive,
    and almost always an incidental radiographic finding. 74% of reported BOS cases in
    the 2016 systematic review (20% bone only plus 54% with both) had osteopoikilosis;
    as with the skin figure this reflects who gets radiographed rather than true
    penetrance. Foci may be absent on radiographs taken in early childhood.
  phenotype_term:
    preferred_term: Osteopoikilosis
    term:
      id: HP:0010739
      label: Osteopoikilosis
  sequelae:
  - target: Arthralgia
    description: >-
      A minority of individuals with osteopoikilosis report joint pain or effusion,
      of unclear relation to the periarticular foci.
    evidence:
    - reference: PMID:25352085
      reference_title: "Osteopoikilosis: report of a familial case and review of the literature."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In this study, we report a 17-year-old boy who suffers from low back pain and has a mother with similar involvement."
      explanation: >-
        A reported case in which osteopoikilosis presented with pain in both an affected
        child and his affected mother. Note this supports co-occurrence, not causation -
        the review itself does not establish that the foci generate the pain.
      directness: INDIRECT
  evidence:
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "BOS combines OPK with connective tissue nevi comprised of collagen and elastin."
    explanation: Defines osteopoikilosis as the skeletal half of the syndrome.
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OPK is another defining characteristic of BOS; a summary of OPK locations revealed that the pelvis is the most commonly affected site."
    explanation: Supports the distribution claim, with the pelvis as the commonest site across reported cases.
- name: Increased Bone Mineral Density
  category: Skeletal
  frequency: FREQUENT
  description: >-
    Focally increased density at the sclerotic foci. Site-averaged densitometry is
    largely unremarkable: in the two biopsied BOS women, lumbar spine areal BMD Z-scores
    were comparable to controls and only the hip was increased, so this is a focal
    finding that should not be read as generalised osteosclerosis.
  phenotype_term:
    preferred_term: Increased bone mineral density
    term:
      id: HP:0011001
      label: Increased bone mineral density
  evidence:
  - reference: PMID:32151766
    reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "aBMD Z-scores were comparable to that of controls in the lumbar spine and increased at the hip."
    explanation: Quantifies the densitometric picture and supports the qualification that the increase is regional rather than generalised.
- name: Increased Number of Elastic Fibers in the Dermis
  category: Dermatological
  frequency: FREQUENT
  description: >-
    The histological signature of the elastoma form of the connective tissue nevus:
    large, thickened, disorganised elastic fibres crowding the reticular dermis,
    demonstrated on Victoria blue or other elastic-tissue stains and easily overlooked
    on routine staining.
  phenotype_term:
    preferred_term: Thickened and increased dermal elastic fibers
    term:
      id: HP:0025164
      label: Increased number of elastic fibers in the dermis
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Victoria blue staining revealed that the dermis of probands 2, 3 (buttocks), 4, 5, and 6 exhibited large, thickened, and haphazardly arrayed elastic fibres (Fig. S1A)."
    explanation: Documents the increased, thickened, disordered dermal elastic fibres in five of six genetically confirmed probands.
- name: Collagenoma
  category: Dermatological
  frequency: OCCASIONAL
  description: >-
    The collagen-predominant form of the connective tissue nevus, in which dense
    hypocellular collagen rather than excess elastic tissue makes up the lesion. In the
    2025 pooled analysis 8% of reported cases had collagenoma alone and 23% a mixed
    collagenoma-plus-elastoma phenotype, so a collagen-only biopsy is fully compatible
    with BOS.
  phenotype_term:
    preferred_term: Collagenoma
    term:
      id: HP:6000022
      label: Collagenoma
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nevertheless, an examination of reported histological manifestations in BOS cases reveals that 8% of cases exclusively presented with collagenoma, while 23% displayed a mixed phenotype encompassing both collagenoma and elastoma."
    explanation: Quantifies collagenoma-only and mixed lesions across the reported literature.
- name: Melorheostosis
  category: Skeletal
  frequency: OCCASIONAL
  description: >-
    Segmental flowing cortical hyperostosis - the dripping-candle-wax radiographic
    appearance - affecting one limb segment asymmetrically, superimposed on the
    symmetric osteopoikilotic foci. Uncommon within LEMD3 kindreds but clinically the
    most consequential skeletal manifestation, since unlike osteopoikilosis it can
    cause pain, deformity and restricted joint motion. Recurrence within a family has
    not been described.
  phenotype_term:
    preferred_term: Melorheostosis
    term:
      id: HP:6000817
      label: Melorheostosis
  evidence:
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Occasionally, a larger area of dense bone in OPK or BOS resembles MEL, a sporadic sclerosing disorder primarily involving cortical bone."
    explanation: Establishes melorheostosis-like cortical disease as an occasional finding in OPK and BOS.
- name: Arthralgia
  category: Musculoskeletal
  frequency: OCCASIONAL
  description: >-
    Joint pain, sometimes with effusion, reported in 15-20% of people with
    osteopoikilosis. The relationship to the periarticular sclerotic foci is not
    established and the association may be partly coincidental, since arthralgia is
    common in the general population and osteopoikilosis is typically discovered on a
    film ordered for joint pain.
  phenotype_term:
    preferred_term: Arthralgia
    term:
      id: HP:0002829
      label: Arthralgia
  evidence:
  - reference: PMID:25352085
    reference_title: "Osteopoikilosis: report of a familial case and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although it is usually asymptomatic, effusion and joint pain can be found in 15-20 % of patients."
    explanation: Source of the 15-20% figure for joint symptoms in osteopoikilosis.
- name: Short Stature
  category: Skeletal
  frequency: OCCASIONAL
  description: >-
    Reduced stature in about 7% of reported BOS cases, all of whom had osteopoikilosis.
    This association was first noted in the 2016 systematic review and is not part of
    the classical description; note also that short stature plus developmental delay
    should prompt evaluation for a larger 12q14 deletion involving genes neighbouring
    LEMD3 rather than being attributed to BOS.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:26708699
    reference_title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients with spinal stenosis (2%) or shortened status (7%) had OPK."
    explanation: Source of the 7% figure and of the observation that it co-occurs with the bone component.
- name: Spinal Canal Stenosis
  category: Skeletal
  frequency: VERY_RARE
  description: >-
    Narrowing of the spinal canal reported in about 2% of BOS cases, all of them with
    osteopoikilosis. Rare enough that it should prompt a search for an alternative
    explanation before being attributed to the syndrome.
  phenotype_term:
    preferred_term: Spinal canal stenosis
    term:
      id: HP:0003416
      label: Spinal canal stenosis
  evidence:
  - reference: PMID:26708699
    reference_title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients with spinal stenosis (2%) or shortened status (7%) had OPK."
    explanation: Source of the 2% spinal stenosis figure among reported BOS cases.
- name: Yellow Papule
  category: Dermatological
  frequency: FREQUENT
  description: >-
    The individual element of the connective tissue nevus as it is usually first seen
    clinically: a small, firm, asymptomatic yellowish papule, appearing in crops that
    may coalesce. Lesions are commonly present for years before the diagnosis is made.
  phenotype_term:
    preferred_term: Yellow papule
    term:
      id: HP:0025507
      label: Yellow papule
  evidence:
  - reference: PMID:20083694
    reference_title: "Buschke-Ollendorff syndrome: absence of LEMD3 mutation in an affected family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe a father and son with multiple yellowish papules and nodules coalescing into cobblestone nevoid plaques consistent with nevus elasticus."
    explanation: Describes the yellowish papular morphology and its coalescence into nevoid plaques.
  - reference: PMID:18986450
    reference_title: "Buschke-Ollendorff syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical examination of the patient showed multiple asymptomatic nodules on both thighs, present since the age of 20 years, which had increased in size and number."
    explanation: Illustrates the asymptomatic, slowly accumulating course of the cutaneous lesions.
histopathology:
- name: Dermal Elastoma
  finding_term:
    preferred_term: elastoma (elastin-rich connective tissue nevus)
  frequency: FREQUENT
  diagnostic: true
  description: >-
    The classical BOS dermal lesion. Elastic-tissue stains (Victoria blue, Verhoeff-van
    Gieson, orcein) show markedly increased, thickened, broad and irregularly arranged
    elastic fibres filling the reticular dermis. No term in the NCIT histopathology
    branch or under HP Abnormal cell morphology names this lesion, so finding_term
    carries a free-text preferred_term only; the corresponding HP phenotype
    (HP:0025164) is bound in the phenotypes block instead.
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Histologically, elastoma is traditionally regarded as the predominant feature of BOS."
    explanation: States the primacy of the elastoma pattern among BOS dermal biopsies.
- name: Dermal Collagenoma
  finding_term:
    preferred_term: collagenoma (collagen-rich connective tissue nevus)
  frequency: OCCASIONAL
  description: >-
    Dense, hypocellular, haphazardly interlacing collagen bundles expanding the dermis
    with normal or reduced elastic tissue, demonstrated on Masson trichrome. May be the
    only pattern present, and may coexist with elastoma in the same patient at
    different sites.
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Masson's trichrome staining indicated collagenoma in probands 3 (foot) and 4 (Fig. S1A)."
    explanation: Documents collagenoma by trichrome staining in two genetically confirmed probands.
- name: Interstitial Dermal Mucin Deposition
  finding_term:
    preferred_term: interstitial dermal mucin deposition
  frequency: FREQUENT
  description: >-
    Increased interstitial mucin between the dermal collagen and elastic fibres,
    demonstrated on Alcian blue. Under-recognised: it was present in every proband of
    the 2025 series, and in at least one reported child it was the only abnormality on
    an otherwise unremarkable biopsy. Its mechanistic relation to LEMD3 loss is unknown.
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Alcian blue staining demonstrated increased interstitial mucin in the reticular dermis of all probands (Fig. S1A)."
    explanation: Establishes dermal mucin as a consistent finding in this series.
  - reference: PMID:32206820
    reference_title: "Buschke-Ollendorff syndrome in a 6-year-old patient: clinical and histopathological aspects of a rare disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A skin biopsy was performed and did not show striking alterations in the number or dimension of the extracellular matrix fibers, but it showed mucin deposition between them, which is compatible with a CTN."
    explanation: >-
      A case in which mucin was the only histological abnormality, supporting the
      warning that a fibre-normal biopsy does not exclude a connective tissue nevus.
- name: Compact Lamellar Sclerotic Bone Nodule
  finding_term:
    preferred_term: osteosclerotic nodule of compact lamellar bone
    term:
      id: NCIT:C69309
      label: Sclerosis
  diagnostic: true
  description: >-
    On undecalcified bone histology and micro-CT the osteopoikilotic focus is a
    stellate nodule of compact lamellar bone within the marrow cavity or on the
    endocortex, formed by modeling-based apposition. Remodelling rate is normal and
    woven bone is absent. The NCIT binding is the generic morphologic finding
    "Sclerosis"; NCIT has no term for this specific lesion.
  evidence:
  - reference: PMID:32151766
    reference_title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In both biopsies, μCT showed trabecular structure comparable to that of controls with stellate shaped sclerotic noduli within the cavity and on the endocortex."
    explanation: Describes the stellate sclerotic nodules and their position within otherwise normal trabecular bone.
imaging_findings:
- name: Multiple Symmetric Periarticular Sclerotic Foci
  modality: XRAY
  spatial_extent: MULTIFOCAL
  diagnostic: true
  description: >-
    The diagnostic plain-film appearance: numerous small, well-defined, homogeneous
    round or ovoid densities clustered around joints and distributed broadly
    symmetrically. Pelvis, hands and wrists, knees and ankles are the highest-yield
    films. Their uniformity and symmetry are what separate them from osteoblastic
    metastatic deposits, which are irregular, asymmetric and axially predominant.
  imaging_finding_term:
    preferred_term: Osteopoikilosis
    term:
      id: HP:0010739
      label: Osteopoikilosis
  evidence:
  - reference: PMID:25352085
    reference_title: "Osteopoikilosis: report of a familial case and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OPK must be in differential diagnosis when multiple, small, well-defined, symmetric bone lesions are identified on plain radiograph to avoid alarming the patient with more serious disease and misdiagnosis."
    explanation: Describes the radiographic pattern and states the clinical reason it matters.
- name: Normal Bone Scintigraphy Over Osteopoikilotic Foci
  modality: OTHER
  description: >-
    Radionuclide bone scanning is normal over osteopoikilotic foci, consistent with the
    histological finding of normal remodelling rate, and this is the single most useful
    discriminator from osteoblastic metastases, which are avid. Note the contrast with
    the melorheostotic lesion, which is metabolically active and does show uptake.
  imaging_finding_term:
    preferred_term: normal radionuclide bone scan over sclerotic foci
  evidence:
  - reference: PMID:25352085
    reference_title: "Osteopoikilosis: report of a familial case and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bone scintigraphy is normal and useful for differential diagnosis."
    explanation: Establishes normal scintigraphy as the discriminating investigation.
- name: Flowing Cortical Hyperostosis
  modality: XRAY
  spatial_extent: SEGMENTAL
  description: >-
    Where melorheostosis accompanies BOS, radiographs show dense, irregular, eccentric
    hyperostosis of the cortex in a segmental distribution, classically likened to
    dripping candle wax, with sharp demarcation between affected and unaffected bone.
  imaging_finding_term:
    preferred_term: Melorheostosis
    term:
      id: HP:6000817
      label: Melorheostosis
  evidence:
  - reference: PMID:30138550
    reference_title: "Distinct Clinical and Pathological Features of Melorheostosis Associated With Somatic MAP2K1 Mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Melorheostosis is a rare hyperostotic disease of the long bones classically characterized by a \"dripping candle-wax\" radiographic appearance."
    explanation: Defines the radiographic appearance this finding records.
genetic:
- name: LEMD3
  gene_term:
    preferred_term: LEMD3
    term:
      id: hgnc:28887
      label: LEMD3
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  association: Causative; heterozygous germline loss of function
  frequency: >-
    Identified in the large majority of clinically diagnosed BOS families, but a
    minority of convincing families have no coding-region variant.
  notes: >-
    LEMD3 (also MAN1) lies at 12q14 and encodes an integral protein of the inner
    nuclear membrane. Reported pathogenic alleles are nonsense, frameshift,
    splice-disrupting or whole-gene deletions distributed across the coding sequence,
    all predicted to remove the C-terminal R-SMAD-interacting region. The CURIE is
    written in the lowercase form this repository uses. Contemporary testing should
    add deletion/duplication analysis to sequencing, and chromosomal microarray is
    warranted when short stature, developmental delay or dysmorphism raises the
    possibility of a contiguous 12q14 deletion rather than an isolated LEMD3 lesion.
  evidence:
  - reference: PMID:15489854
    reference_title: "Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A genome-wide linkage analysis in these families, followed by the identification of a microdeletion in an unrelated individual with these diseases, allowed us to map the gene that is mutated in osteopoikilosis."
    explanation: The mapping and gene-identification step that established LEMD3 as causative.
  - reference: PMID:27382493
    reference_title: "Mutation in LEMD3 (Man1) Associated with Osteopoikilosis and Late-Onset Generalized Morphea: A New Buschke-Ollendorf Syndrome Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two additional family members were found to have osteopoikilosis and carry the same LEMD3 mutation."
    explanation: Cosegregation of an LEMD3 nonsense allele with osteopoikilosis across a family.
  - reference: PMID:26694706
    reference_title: "Identification of a novel LEMD3 Y871X mutation in a three-generation family with osteopoikilosis and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mutation co-segregates with the osteopoikilosis phenotype and was not found in 100 ethnically matched controls."
    explanation: Cosegregation across three generations with control screening, supporting causality of truncating LEMD3 alleles.
  - reference: PMID:20083694
    reference_title: "Buschke-Ollendorff syndrome: absence of LEMD3 mutation in an affected family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Absence of LEMD3 mutation in the exons and splice sites of a family with BOS suggests that there is genetic heterogeneity for this disorder."
    explanation: >-
      A clinically unambiguous BOS family with no LEMD3 coding variant, supporting the
      qualification that LEMD3 does not account for every case.
diagnosis:
- name: Clinical and Radiographic Diagnosis
  description: >-
    BOS is diagnosed from the combination of connective tissue nevi and radiographic
    osteopoikilosis, usually with a supporting family history. Plain radiographs of the
    pelvis, hands and wrists, knees and ankles are the highest-yield screen; CT adds
    little in typical disease and PET/MRI is unnecessary. Because expressivity is
    variable, a first-degree relative with only one component still warrants
    consideration, and a negative childhood radiograph does not exclude osteopoikilosis
    that appears later.
  diagnosis_term:
    preferred_term: plain radiography
    term:
      id: NCIT:C38101
      label: X-Ray Imaging
  evidence:
  - reference: PMID:26708699
    reference_title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A family history was noted in 92% of cases."
    explanation: Supports the weight given to family history in recognising the syndrome.
  - reference: PMID:18986450
    reference_title: "Buschke-Ollendorff syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "After a minor trauma, radiologic examination of the left ankle of a 39-year-old woman revealed features of osteopoikilosis."
    explanation: Illustrates the typical route to diagnosis - an incidental radiograph taken for an unrelated reason.
- name: Bone Scintigraphy to Exclude Osteoblastic Metastasis
  description: >-
    The clinically consequential mistake in this disease is reading the sclerotic foci
    as osteoblastic metastases and launching an oncological workup. Radionuclide bone
    scanning resolves it: osteopoikilotic foci are cold, metastatic deposits are avid.
    This is the highest-value single investigation when the radiographic finding is
    encountered without a known diagnosis.
  diagnosis_term:
    preferred_term: radionuclide bone scan
    term:
      id: NCIT:C17646
      label: Bone Scan
  evidence:
  - reference: PMID:25352085
    reference_title: "Osteopoikilosis: report of a familial case and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It may be confused with other conditions, such as osteoblastic metastases."
    explanation: Names the differential this investigation exists to settle.
  - reference: PMID:27267960
    reference_title: "The Buschke-Ollendorff syndrome: a case report of simultaneous osteo-cutaneous malformations in the hand."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A correct diagnosis of Buschke-Ollendorff syndrome is necessary to spare patients from expensive investigations and to provide reassurance about the benign nature of the disease."
    explanation: States the clinical value of arriving at the diagnosis - avoiding unnecessary investigation.
- name: Skin Biopsy with Elastic-Fiber and Mucin Staining
  description: >-
    Reserved for atypical or diagnostically uncertain lesions. Request elastic-tissue
    staining (Victoria blue, Verhoeff-van Gieson or orcein), trichrome and Alcian blue
    alongside routine histology: routine haematoxylin and eosin alone can look
    unremarkable, and the pattern may be elastoma, collagenoma, mixed, or mucin-rich.
    A non-classic biopsy therefore does not exclude the diagnosis.
  diagnosis_term:
    preferred_term: skin biopsy
    term:
      id: NCIT:C51692
      label: Skin Biopsy
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These results underscore the pathological heterogeneity of BOS."
    explanation: Supports ordering the full panel of stains rather than relying on a single classic pattern.
- name: LEMD3 Molecular Genetic Testing
  description: >-
    Sequencing of the LEMD3 coding exons and splice boundaries confirms the diagnosis
    and enables cascade testing of relatives; deletion/duplication analysis should be
    added, since whole-gene deletions occur. A negative result does not overturn a
    convincing osteocutaneous phenotype - genetically unexplained BOS families are
    documented. Screening is specifically recommended in atypical presentations that
    combine fibrotic skin lesions with a spotted radiographic pattern.
  diagnosis_term:
    preferred_term: LEMD3 sequence analysis
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  evidence:
  - reference: PMID:27267960
    reference_title: "The Buschke-Ollendorff syndrome: a case report of simultaneous osteo-cutaneous malformations in the hand."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In atypical cases of simultaneous occurrence of fibrotic skin lesions and a spotted pattern in the X-ray we recommend the genetic screening of the LEMD3 gene."
    explanation: Explicit recommendation for LEMD3 screening in the presentation this entry describes.
differential_diagnoses:
- name: Osteoblastic Bone Metastases
  description: >-
    The differential that matters. Metastatic osteoblastic deposits are irregular,
    asymmetric, axially predominant and scintigraphically avid; osteopoikilotic foci
    are uniform, periarticular, broadly symmetric and cold on bone scan.
  distinguishing_features:
  - Symmetric periarticular distribution versus irregular axial distribution
  - Normal bone scintigraphy versus increased radiotracer uptake
  - Stable over decades versus progressive
  - Family history of the same radiographic pattern
  evidence:
  - reference: PMID:25352085
    reference_title: "Osteopoikilosis: report of a familial case and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Diagnosis is usually made incidentally according to radiographs."
    explanation: Supports the framing that this differential is typically encountered on an incidentally obtained film.
- name: Sporadic Isolated Melorheostosis
  description: >-
    Melorheostosis without osteopoikilosis, occurring sporadically without familial
    clustering. This is a genetically distinct disease driven by post-zygotic
    activating MAP2K1 mutation restricted to the affected bone, not a forme fruste of
    BOS. Repeated LEMD3 sequencing of such patients - including of lesional bone and
    skin - has been negative.
  distinguishing_features:
  - No connective tissue nevi and no osteopoikilotic foci elsewhere in the skeleton
  - Sporadic occurrence with no family history
  - Somatic mosaic MAP2K1 variant in affected but not unaffected bone
  - Germline LEMD3 sequencing negative
  evidence:
  - reference: PMID:29643386
    reference_title: "Somatic activating mutations in MAP2K1 cause melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using whole exome sequencing, we identify somatic mosaic MAP2K1 mutations in affected, but not unaffected, bone of eight unrelated patients with melorheostosis."
    explanation: Establishes the distinct somatic MAP2K1 aetiology of sporadic melorheostosis.
  - reference: PMID:16470551
    reference_title: "Germline LEMD3 mutations are rare in sporadic patients with isolated melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Somatic mosaicism for a LEMD3 mutation in the latter group was also not observed, and therefore we must conclude that the genetic defect in the majority of sporadic and isolated melorheostosis remains unknown."
    explanation: >-
      The negative LEMD3 result, germline and somatic, in sporadic isolated
      melorheostosis - written before MAP2K1 was found, and the reason the field went
      looking.
- name: 12q14 Microdeletion Syndrome
  description: >-
    A contiguous-gene deletion spanning LEMD3 and its neighbours (including HMGA2),
    producing osteopoikilosis together with primordial short stature and developmental
    delay. Suspect it when a patient with osteopoikilosis also has growth failure or
    cognitive impairment, and investigate with chromosomal microarray rather than
    LEMD3 sequencing alone.
  distinguishing_features:
  - Proportionate short stature and developmental delay accompanying the bone findings
  - Deletion detectable on chromosomal microarray, not on LEMD3 sequencing
  - Connective tissue nevi not a consistent feature
  evidence:
  - reference: PMID:19277063
    reference_title: "Refinement of the 12q14 microdeletion syndrome: primordial dwarfism and developmental delay with or without osteopoikilosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In their studies on the molecular basis of osteopoikilosis, Menten et al have identified three individuals with microdeletions on chromosome 12q14.4, which removed several genes including LEMD3, the osteopoikilosis gene. In addition to osteopoikilosis, affected individuals had growth retardation and developmental delay."
    explanation: >-
      Establishes the contiguous-deletion entity in which osteopoikilosis arrives with
      growth retardation and developmental delay, which is why those features should
      prompt an array rather than being attributed to Buschke-Ollendorff syndrome.
  - reference: PMID:19277063
    reference_title: "Refinement of the 12q14 microdeletion syndrome: primordial dwarfism and developmental delay with or without osteopoikilosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The 12q14 deletion did not include LEMD3, and no signs of osteopoikilosis were observed on skeletal radiographs."
    explanation: >-
      Shows the deletion boundary determines whether osteopoikilosis is present,
      confirming that the skeletal component tracks LEMD3 while the growth and
      developmental features track neighbouring genes.
treatments:
- name: Observation and Reassurance
  description: >-
    For the great majority of patients this is the whole of management. Osteopoikilotic
    foci are benign, non-progressive and asymptomatic and require no intervention, and
    most connective tissue nevi need none either. The active work is explaining the
    radiographic findings so that neither the patient nor a future clinician mistakes
    them for malignancy, and documenting the diagnosis where it will be found again.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OPK is an autosomal dominant, usually benign, skeletal dysplasia featuring multiple, small, especially metaphyseal, oval or round, dense trabecular foci distributed symmetrically throughout the skeleton."
    explanation: Establishes the benign nature of the skeletal lesions that justifies observation over intervention.
- name: Genetic Counselling and Cascade Evaluation
  description: >-
    Autosomal dominant transmission with a 50% recurrence risk per pregnancy, but
    counselling must convey that the phenotype in an inheriting child cannot be
    predicted from the parent's: the same allele produces skin-only, bone-only, full
    and clinically silent presentations within one family. Cascade radiographic and
    dermatological evaluation of relatives is useful mainly to spare them an
    oncological workup later. Because the causative gene is known, prenatal
    diagnosis and preimplantation genetic testing are technically available once a
    familial LEMD3 variant has been identified; counselling should say so while
    setting it against the condition's generally benign course and the fact that
    the severity in an inheriting child cannot be predicted, so the decision is not
    the one it would be for a progressive or life-limiting disease.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:19438932
    reference_title: "Novel and recurrent germline LEMD3 mutations causing Buschke-Ollendorff syndrome and osteopoikilosis but not isolated melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We investigated LEMD3 in a two-generation BOS family showing an extremely variable expression of the disease, in a sporadic patient with skin features of BOS, and in an additional subject with isolated melorheostosis."
    explanation: Documents the extreme within-family variability that counselling has to convey.
- name: Analgesic Therapy for Musculoskeletal Pain
  description: >-
    Simple analgesics or anti-inflammatory agents for the minority who have joint pain
    or effusion, or pain from a melorheostotic segment. Symptomatic only; no agent
    modifies the underlying bone lesion.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: analgesic agent
      term:
        id: NCIT:C241
        label: Analgesic Agent
  target_phenotypes:
  - preferred_term: Arthralgia
    term:
      id: HP:0002829
      label: Arthralgia
  evidence:
  - reference: PMID:25352085
    reference_title: "Osteopoikilosis: report of a familial case and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although it is usually asymptomatic, effusion and joint pain can be found in 15-20 % of patients."
    explanation: >-
      Establishes the minority with joint symptoms who need analgesia; the paper does
      not specify a regimen.
- name: Surgical Excision of Symptomatic Connective Tissue Nevi
  description: >-
    Excision may be considered for a nevus that is painful, mechanically limiting
    (hand and plantar lesions in particular) or cosmetically distressing. Counsel about
    scarring first: hypertrophic scarring after skin incision was recorded in four of
    six probands in the 2025 series, and in one reported case the excision itself
    produced a disabling contracture. Outcome evidence is limited to case reports.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: surgical excision
    term:
      id: NCIT:C15232
      label: Excision
  evidence:
  - reference: PMID:40195882
    reference_title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Notably, 4 probands developed scars after skin incisions (Fig. 1A)."
    explanation: The scarring risk that has to be weighed before excising a benign lesion.
  - reference: PMID:27267960
    reference_title: "The Buschke-Ollendorff syndrome: a case report of simultaneous osteo-cutaneous malformations in the hand."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two sclerotic skin lesions had been excised 7 years before because of consecutive skin contracture."
    explanation: A reported case in which excision was undertaken for contracture, illustrating both the indication and the sequela.
- name: Corrective Orthopaedic Surgery
  description: >-
    Reserved for substantial fixed deformity, joint impingement or nerve entrapment,
    which in practice means the melorheostotic rather than the osteopoikilotic
    skeleton. Reported interventions include corrective osteotomy for a digital
    deformity. Contracture recurrence after soft-tissue surgery in extensive
    melorheostosis is a recognised problem.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: orthopaedic surgical procedure
    term:
      id: NCIT:C16186
      label: Orthopedic Surgical Procedure
  evidence:
  - reference: PMID:27267960
    reference_title: "The Buschke-Ollendorff syndrome: a case report of simultaneous osteo-cutaneous malformations in the hand."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A corrective osteotomy of the thumb was carried out due to the patients discomfort."
    explanation: A reported corrective osteotomy in a genetically confirmed BOS patient.
  - reference: PMID:30989250
    reference_title: "Melorheostosis and Osteopoikilosis: A Review of Clinical Features and Pathogenesis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Surgical intervention may be required for those with large bone growths, nerve entrapments, joint impingement syndromes or major limb deformities."
    explanation: Sets out the indications for surgery in the melorheostotic subset.
- name: Bisphosphonate Therapy for Symptomatic Melorheostosis
  description: >-
    Used for pain in symptomatic melorheostosis, on weak evidence. Not indicated for
    osteopoikilosis or for the cutaneous lesions, and there is no reason to expect
    benefit there - the osteopoikilotic nodule has a normal remodelling rate, so an
    antiresorptive has no obvious target. Included because it is the one pharmacological
    option that appears in the sclerosing-bone-disease literature; it is not BOS therapy.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: bisphosphonate therapy
    term:
      id: NCIT:C198585
      label: Bisphosphonate Therapy
  target_phenotypes:
  - preferred_term: Melorheostosis
    term:
      id: HP:6000817
      label: Melorheostosis
  evidence:
  - reference: PMID:30989250
    reference_title: "Melorheostosis and Osteopoikilosis: A Review of Clinical Features and Pathogenesis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Medical treatments include bisphosphonates, but definitive guidance on their use is lacking given the small number of patients that have been studied."
    explanation: Supports both the use and the explicit weakness of the evidence base for it.
animal_models:
- name: Lemd3+/GT heterozygous gene-trap mouse
  species: Mouse
  genotype: Lemd3 heterozygous gene-trap (Lemd3+/GT)
  category: Genetically engineered
  description: >-
    A BayGenomics gene-trap allele, studied heterozygously as the direct genetic
    counterpart of human LEMD3 haploinsufficiency. Assessed by high-resolution
    micro-CT with full 3D cortical and trabecular histomorphometry, plain radiography
    read by a trained radiologist, and conventional histology. The result was negative
    on every measure. This is a substantive negative finding, not a failed experiment:
    the same allelic state that reliably produces osteopoikilosis in humans produces no
    skeletal lesion in the mouse, so the species is not dosage-equivalent at this locus
    and there is at present no animal model of the human bone phenotype.
  genes:
  - preferred_term: Lemd3
    term:
      id: hgnc:28887
      label: LEMD3
  publication: PMID:19862465
  modeled_mechanisms:
  - target: Focal Trabecular Osteosclerotic Nodule Formation
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    model_scale: TISSUE
    description: >-
      Heterozygous Lemd3 gene-trap mice form no osteopoikilosis-like sclerotic nodules
      on radiography, micro-CT or histology.
    limitations: >-
      The mouse does not reproduce the phenotype the model was built to study, so it
      cannot be used to test therapeutic or mechanistic hypotheses about the human
      lesion. It remains informative only as evidence that murine skeletal tissue
      tolerates a halved Lemd3 dose that humans do not. The study examined heterozygotes
      only, at the ages reported, and did not test whether an aged or challenged animal
      might eventually develop foci.
    divergences:
    - divergence_type: SPECIES_MISMATCH
      materiality: INVALIDATING
      description: >-
        Mouse skeletal tissue appears insensitive to the 50% reduction in Lemd3 dose
        that produces focal osteosclerosis in humans. The failure is at the level of
        the organism's response to the genotype, not of the genotype itself: the allele
        is the correct one.
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: >-
        The cutaneous arm of the syndrome - dermal connective tissue nevi - was not
        assessed at all in this study, so the model is silent on the skin phenotype
        rather than negative for it.
    readouts:
    - name: Cortical and trabecular bone histomorphometry by micro-CT
      target: Focal Trabecular Osteosclerotic Nodule Formation
      interpretation: >-
        Percent bone volume, bone surface/volume ratio, trabecular thickness,
        separation, number, pattern factor, structure model index and fractal dimension
        were all statistically indistinguishable from wild type. Direction is left unset
        because the measurement showed no change in either direction.
      evidence:
      - reference: PMID:19862465
        reference_title: "The heterozygous Lemd3 +/GT mouse is not a murine model for osteopoikilosis in humans."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "No significant differences were found after a t-test statistical analysis."
        explanation: Reports the negative quantitative micro-CT result for this readout.
    - name: Radiographic and histological survey for osteopoikilotic lesions
      target: Focal Trabecular Osteosclerotic Nodule Formation
      interpretation: >-
        Neither radiography read by a trained radiologist nor conventional histology
        identified lesions typical of osteopoikilosis.
      evidence:
      - reference: PMID:19862465
        reference_title: "The heterozygous Lemd3 +/GT mouse is not a murine model for osteopoikilosis in humans."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "X-ray images were evaluated by a trained radiologist, but no typical osteopoikilosis lesions could be recognized."
        explanation: The radiographic arm of the negative result.
    evidence:
    - reference: PMID:19862465
      reference_title: "The heterozygous Lemd3 +/GT mouse is not a murine model for osteopoikilosis in humans."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We conclude that the heterozygous Lemd3 gene-trapped mouse is not a good model to study osteopoikilosis and the Buschke-Ollendorff syndrome."
      explanation: The authors' own conclusion, which is the FAILS_TO_RECAPITULATE claim this link records.
  evidence:
  - reference: PMID:19862465
    reference_title: "The heterozygous Lemd3 +/GT mouse is not a murine model for osteopoikilosis in humans."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Also, histological analysis did not reveal lesions typical for osteopoikilosis."
    explanation: The histological arm of the negative result, supporting the model entry as a whole.
- name: Man1 Smad-interacting-domain homozygous deletion mouse
  species: Mouse
  genotype: Man1 (Lemd3) homozygous deletion of the Smad-interacting domain
  category: Genetically engineered
  description: >-
    Embryos lacking the MAN1 Smad-interacting domain, used to show what unopposed
    Smad2/3 signalling does in vivo. They die at midgestation from a failure of
    vascular remodelling: the primary capillary plexus forms but is not remodelled,
    mural cell recruitment fails, Tgfb1 expression rises and Smad2/3 signalling is
    abnormally activated, with increased extracellular matrix deposition. The tissue is
    vascular rather than dermal or skeletal and the genotype is homozygous rather than
    heterozygous, so this is evidence about the pathway, not about the human disease.
  genes:
  - preferred_term: Lemd3
    term:
      id: hgnc:28887
      label: LEMD3
  publication: PMID:16943282
  modeled_mechanisms:
  - target: Increased TGF-beta-SMAD2/3 Transcriptional Output
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      Loss of the Smad-interacting domain activates Smad2/3 signalling in vivo and
      increases extracellular matrix deposition, which is the molecular claim this
      pathophysiology node makes.
    limitations: >-
      Homozygous rather than the heterozygous state that causes human disease, and
      embryonic-lethal, so it says nothing about the postnatal, focal, tissue-restricted
      lesions of BOS. The phenotype observed is vascular; neither bone nor dermis was
      examined.
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: >-
        Bone and dermis, the two tissues in which the human lesion appears, are outside
        the model's boundary; only the embryonic vasculature was studied.
    - divergence_type: TEMPORAL_SCOPE
      materiality: QUALIFYING
      description: >-
        The animal dies at midgestation, so the model covers only embryogenesis, while
        osteopoikilotic foci and connective tissue nevi accumulate postnatally over
        years.
    evidence:
    - reference: PMID:16943282
      reference_title: "Man1, an inner nuclear membrane protein, regulates vascular remodeling by modulating transforming growth factor beta signaling."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Man1-deficient embryos die at midgestation because of defects in embryonic vasculature; the primary capillary plexus forms, but subsequent remodeling is perturbed."
      explanation: Establishes what the model actually shows, and the lethality that bounds what it can be used for.
  evidence:
  - reference: PMID:16943282
    reference_title: "Man1, an inner nuclear membrane protein, regulates vascular remodeling by modulating transforming growth factor beta signaling."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Here, we show that Man1 regulates vascular remodeling by analyzing Man1-deficient embryos lacking the Smad interacting domain."
    explanation: >-
      Defines the allele - deletion of the Smad-interacting domain specifically - which
      is what makes this animal informative about the SMAD-antagonism arm of the human
      mechanism rather than about MAN1 in general.
- name: XMAN1 gain- and loss-of-function Xenopus embryo
  species: African clawed frog
  genotype: XMAN1 overexpression and antisense morpholino knockdown in Xenopus laevis embryos
  category: Genetically engineered
  description: >-
    The developmental system in which MAN1's BMP-antagonising function was first
    demonstrated. Overexpressed XMAN1 blocks BMP target genes and suppresses a
    BMP-responsive promoter; morpholino knockdown of endogenous XMAN1 reduces anterior
    neuroectoderm. Deletion analysis localises both the neuralising and BMP-antagonising
    activities to the C-terminal region that binds Smad1, Smad5 and Smad8 - the region
    human truncating LEMD3 alleles delete.
  genes:
  - preferred_term: LEMD3
    term:
      id: hgnc:28887
      label: LEMD3
  publication: PMID:12642484
  modeled_mechanisms:
  - target: Loss of Nuclear Envelope R-SMAD Antagonism
    relationship: PERTURBS
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      Bidirectional manipulation of MAN1 dose in a whole embryo, reading out BMP target
      gene expression, which is the mechanism this node asserts is lost in patients.
    limitations: >-
      A developmental patterning assay in an amphibian embryo, not a disease model:
      neither bone nor dermal connective tissue is assayed, and the perturbations are
      overexpression and near-complete knockdown rather than the 50% reduction seen in
      patients.
    divergences:
    - divergence_type: SPECIES_MISMATCH
      materiality: QUALIFYING
      description: >-
        Xenopus early embryogenesis. The Smad-binding function is conserved, but the
        tissue context (neuroectoderm patterning) has no counterpart in the human
        disease.
    - divergence_type: PROXY_QUANTITY
      materiality: QUALIFYING
      description: >-
        The measured quantity is BMP target-gene expression (Xhox3, Msx1) and a Xvent2
        reporter, standing in for the human node's quantity, which is the amount of
        R-SMAD sequestered and dephosphorylated at the inner nuclear membrane.
    evidence:
    - reference: PMID:12642484
      reference_title: "XMAN1, an inner nuclear membrane protein, antagonizes BMP signaling by interacting with Smad1 in Xenopus embryos."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Interference with endogenous XMAN1 functions with antisense morpholino oligos leads to the reduction of anterior neuroectoderm."
      explanation: The loss-of-function arm of the manipulation, showing that endogenous MAN1 dose matters in vivo.
  evidence:
  - reference: PMID:12642484
    reference_title: "XMAN1, an inner nuclear membrane protein, antagonizes BMP signaling by interacting with Smad1 in Xenopus embryos."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Using a Xenopus expression screening approach with an anterior neuroectoderm cDNA library, we have identified an inner nuclear membrane protein, XMAN1, as a novel neuralizing factor that is encoded by the Xenopus ortholog of human MAN1."
    explanation: >-
      Establishes XMAN1 as the Xenopus orthologue of human MAN1, which is what licenses
      using this system to interrogate the human protein's function.
discussions:
- discussion_id: melorheostosis_attribution
  kind: CONTROVERSY
  status: OPEN
  prompt: >-
    Is melorheostosis a manifestation of LEMD3 loss of function, or a separate disease
    that happens to look similar and occasionally co-occurs?
  attaches_to:
  - pathophysiology#Segmental Cortical Hyperostosis
  - phenotypes#Melorheostosis
  - has_subtypes#BOS with Melorheostosis
  rationale: >-
    The 2004 gene-discovery paper put melorheostosis in its title alongside
    osteopoikilosis and BOS, and that framing persisted for years. It was wrong as a
    general claim, and the correction matters both nosologically and therapeutically.

    What is settled: (i) some individuals in LEMD3 kindreds do develop segmental
    cortical hyperostosis read as melorheostosis, and they carry the family's germline
    LEMD3 allele; (ii) patients with sporadic isolated melorheostosis - no
    osteopoikilosis, no family history - repeatedly test negative for germline LEMD3
    variants, and negative for LEMD3 somatic mosaicism in lesional bone and skin; and
    (iii) most such patients instead carry a post-zygotic activating MAP2K1 variant
    confined to the affected bone, with mutant allele fractions of 1-34% and absent
    from contralateral unaffected bone and from blood. So sporadic melorheostosis is a
    somatic MEK1 mosaic disorder and is not BOS.

    What is not settled is the LEMD3-associated form. Within a kindred the germline
    allele is shared by everyone, yet only one member develops the segmental lesion, so
    the genotype alone cannot be the explanation. The long-standing hypothesis is a
    somatic second hit at LEMD3 in the affected segment, but that has been looked for
    and not found. Whether the LEMD3-associated segmental lesion is mechanistically the
    same entity as MAP2K1 melorheostosis, or a distinct lesion that resembles it
    radiographically, is unresolved - the two are convergent at the level of "excess
    cortical bone in an asymmetric focal pattern" and have not been compared
    histologically within one study.

    Curation consequence: this entry models the segmental hyperostosis as a
    within-syndrome node of hypothetical mechanism, keeps sporadic melorheostosis in
    differential_diagnoses rather than in the pathograph, and does not assert that
    LEMD3 causes melorheostosis in general.
  evidence:
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We confirm that OPK and BOS individuals, including those with MEL-like lesions, have heterozygous, deactivating, germline LEMD3 mutations. However, MEL remains of unknown etiology."
    explanation: The study that separated the two claims - LEMD3 explains OPK/BOS including their MEL-like lesions, but not melorheostosis as an entity.
  - reference: PMID:17087626
    reference_title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "However, no LEMD3 mutation was found for any other patient, including all four with sporadic MEL."
    explanation: >-
      Refutes the proposition that LEMD3 loss of function explains sporadic
      melorheostosis - the claim carried in the 2004 paper's title.
  - reference: PMID:19438932
    reference_title: "Novel and recurrent germline LEMD3 mutations causing Buschke-Ollendorff syndrome and osteopoikilosis but not isolated melorheostosis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "The present study supports the general conclusion that LEMD3 mutations do not contribute to isolated sporadic melorheostosis."
    explanation: Independent replication of the negative LEMD3 result in isolated melorheostosis.
  - reference: PMID:29643386
    reference_title: "Somatic activating mutations in MAP2K1 cause melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The activating mutations (Q56P, K57E and K57N) cluster tightly in the MEK1 negative regulatory domain."
    explanation: Identifies the actual somatic driver of sporadic melorheostosis, in a gene unrelated to LEMD3.
  - reference: PMID:30989250
    reference_title: "Melorheostosis and Osteopoikilosis: A Review of Clinical Features and Pathogenesis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recent studies of melorheostosis lesional tissue indicate that most cases arise from somatic MAP2K1 mutations although a small number may arise from other genes in related pathways, such as KRAS."
    explanation: >-
      Contemporary review position, and the qualification that MAP2K1 does not account
      for every case either.
  - reference: PMID:17622481
    reference_title: "A novel LEMD3 mutation common to patients with osteopoikilosis with and without melorheostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The nature of the additional genetic and/or environmental influences required for the development of melorheostosis in those with osteopoikilosis requires further investigation."
    explanation: States the residual open question about the LEMD3-associated segmental lesion that this discussion records as unresolved.
- discussion_id: lemd3_tissue_selectivity
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    LEMD3 is expressed in essentially every nucleated cell and the loss-of-function
    allele is present in every cell. Why are the lesions confined to bone and dermis,
    and why are they focal within those tissues rather than uniform?
  attaches_to:
  - pathophysiology#Increased BMP-SMAD1/5/8 Transcriptional Output
  - pathophysiology#Dermal Fibroblast Elastin and Collagen Overproduction
  rationale: >-
    This is the central unexplained feature of the disease and it has two parts.

    Tissue selectivity: a ubiquitous 50% reduction produces disease only where BMP and
    TGF-beta signalling sets matrix output - osteoblast lineage and dermal fibroblast.
    A plausible reading is that these are simply the tissues whose phenotype is most
    sensitive to SMAD dose, but that has not been tested; no BOS-specific
    transcriptomic, proteomic or single-cell dataset exists in any tissue.

    Focality within a tissue: this is the harder half. Cultured fibroblasts from
    clinically uninvolved BOS skin already overproduce tropoelastin more than
    three-fold, so the cellular defect is present where there is no lesion, and
    something else decides where a nevus forms. The same puzzle applies in bone, where
    the sclerotic nodules occupy a small fraction of a uniformly haploinsufficient
    skeleton. Two candidate explanations are on the table and neither has been tested
    in BOS tissue: a somatic second event confined to the lesion (searched for in
    LEMD3 and not found), or a local modifier such as matrix stiffness - the
    LEMD3-SMAD2/3 interaction weakens as stiffness rises, which would make the
    haploinsufficient cell progressively less able to restrain TGF-beta in exactly the
    stiffening matrix it is building, a plausible focal positive-feedback loop.
  evidence:
  - reference: PMID:1629625
    reference_title: "Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In a second patient, whose involvement was nearly complete, elastin production was high in involved areas and less so in completely involved skin."
    explanation: >-
      Reports elastin production varying between skin sites within one patient, which
      is the observation the focality question rests on.
  - reference: PMID:30108174
    reference_title: "LEM domain-containing protein 3 antagonizes TGFβ-SMAD2/3 signaling in a stiffness-dependent manner in both the nucleus and cytosol."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Using human lung biopsies, we observed that these nuclear and cytosolic interactions are also present in tissue and found that fibrotic tissues exhibit locally diminished and cytoplasmically shifted LEMD3-SMAD2/3 interactions, as noted in vitro"
    explanation: >-
      Shows locally diminished LEMD3-SMAD2/3 interaction in stiffened human tissue,
      the basis for the matrix-stiffness hypothesis offered here as one candidate
      explanation for focality.
- discussion_id: lemd3_negative_bos_families
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What causes Buschke-Ollendorff syndrome in families with an unambiguous
    osteocutaneous phenotype and no detectable LEMD3 coding variant?
  attaches_to:
  - genetic#LEMD3
  rationale: >-
    At least one family with textbook BOS - father and son with nevus elasticus plus
    radiographic osteopoikilosis - has been sequenced across all LEMD3 exons and splice
    sites with no variant found. Candidate explanations that have not been excluded
    include a deep intronic or regulatory variant, a copy-number change missed by
    sequencing (deletion/duplication analysis was not routine at the time), and locus
    heterogeneity involving another component of the nuclear-envelope SMAD-terminating
    machinery. The practical consequence is already established: a negative LEMD3 test
    does not overturn a convincing phenotype.
  evidence:
  - reference: PMID:20083694
    reference_title: "Buschke-Ollendorff syndrome: absence of LEMD3 mutation in an affected family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although the clinical findings are diagnostic of Buschke-Ollendorf syndrome, analysis of the LEMD3 gene showed no exonic mutations."
    explanation: The mutation-negative family that defines this gap.
- discussion_id: bos_no_animal_model
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Heterozygous Lemd3 mice have the same allelic state as human patients and show no
    skeletal phenotype at all. Is murine bone genuinely insensitive to Lemd3 dosage, or
    was the phenotype missed?
  attaches_to:
  - pathophysiology#Focal Trabecular Osteosclerotic Nodule Formation
  - animal_models#Lemd3+/GT heterozygous gene-trap mouse
  rationale: >-
    Human LEMD3 haploinsufficiency reliably produces osteopoikilosis. The heterozygous
    Lemd3 gene-trap mouse, examined by radiography, quantitative micro-CT
    histomorphometry across eight structural parameters, and conventional histology,
    showed nothing. The mismatch is not evidence-absent - the experiment was done and
    was negative - it is a translational validity problem, and it is the reason no
    animal model of the human bone phenotype exists. Alternatives that would
    discriminate: whether murine bone simply tolerates a halved dose (a real species
    difference in SMAD dose sensitivity), whether the murine lesion requires a longer
    lifespan or a mechanical challenge to appear, or whether the gene-trap allele is
    hypomorphic rather than null and the effective dose reduction was smaller than in
    patients. Until this is resolved, mechanistic and therapeutic hypotheses about the
    human lesion cannot be tested in vivo; a conditional or knock-in allele in the
    osteoblast lineage, or a patient-derived iPSC osteoblast system, is the obvious
    next step.
  proposed_experiments:
  - experiment_id: conditional_lemd3_osteoblast_lineage
    name: Osteoblast-lineage conditional Lemd3 inactivation
    description: >-
      Inactivate Lemd3 conditionally in the osteoblast/bone-lining lineage and age the
      animals, testing whether tissue-restricted and more complete loss produces focal
      sclerotic nodules that the germline heterozygote does not.
    would_support:
    - pathophysiology#Bone Lining Cell Activation and Modeling-Based Bone Formation
    supporting_outcome:
    - >-
      Discrete lamellar sclerotic nodules appear within trabecular bone on micro-CT,
      with modeling-based apposition and normal remodelling rate on dynamic
      histomorphometry, mirroring the human lesion.
    refuting_outcome:
    - >-
      No focal sclerosis develops even with complete lineage-restricted loss and
      ageing, which would move the explanation away from osteoblast-autonomous SMAD
      dose and toward a systemic or developmental requirement.
  evidence:
  - reference: PMID:19862465
    reference_title: "The heterozygous Lemd3 +/GT mouse is not a murine model for osteopoikilosis in humans."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "To investigate whether the heterozygous gene-trapped mouse is a good model for osteopoikilosis in humans, we studied these mice radiologically with high-resolution micro-computed tomography (microCT) and histologically."
    explanation: Describes the study design, establishing that the negative result comes from a purpose-built and adequately powered comparison rather than an incidental observation.
- discussion_id: bos_cognitive_delay_association
  kind: OPEN_QUESTION
  status: OPEN
  prompt: >-
    Is cognitive delay part of Buschke-Ollendorff syndrome, or an artefact of
    ascertainment and of contiguous 12q14 deletions being counted as BOS?
  attaches_to:
  - phenotypes#Short Stature
  - genetic#LEMD3
  rationale: >-
    A 2016 systematic review reported cognitive delays in 50% of its own single-centre
    cohort and in 17% of literature cases published from 2007 onwards, with none
    reported before 2007. That temporal pattern is the problem: it is exactly what
    reporting bias looks like, and 2007 is also roughly when microarray testing became
    routine, so cases with a contiguous 12q14 deletion - which removes HMGA2 and other
    neighbours and does cause developmental delay and short stature - would have begun
    entering the BOS literature. A single-child 2024 preprint describing intellectual
    disability adds nothing decisive. No cognitive phenotype is deliberately curated in
    this entry's phenotypes block on this evidence. Resolving it needs
    neurodevelopmental assessment of a molecularly defined cohort with contiguous
    deletions excluded by array.
  evidence:
  - reference: PMID:26708699
    reference_title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, 50% of the cohort from HSC had cognitive delays, and only cases from 2007 onwards reported cognitive delays (the prevalence was 17% among those cases)."
    explanation: >-
      The observation itself, including the post-2007 restriction that is the main
      reason to treat it as an ascertainment artefact rather than a syndrome feature.
references:
- reference: PMID:15489854
  title: "Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis."
  findings:
  - statement: >-
      Gene-discovery study. Heterozygous LEMD3 loss-of-function variants in osteopoikilosis
      and BOS families; LEMD3 interacts with BMP- and activin/TGF-beta-activated SMADs and
      antagonises both pathways in human cells. Its title also attributes melorheostosis to
      LEMD3, a claim later refuted for the sporadic form - see the
      "melorheostosis_attribution" discussion.
- reference: PMID:17087626
  title: "Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis."
  findings:
  - statement: >-
      Sequenced 11 individuals with sclerosing bone disorders. Germline LEMD3 mutations in
      OPK and BOS families including one with MEL-like lesions, and in none of the four
      with sporadic melorheostosis.
- reference: PMID:29643386
  title: "Somatic activating mutations in MAP2K1 cause melorheostosis."
  findings:
  - statement: >-
      Paired affected/unaffected bone exome sequencing in 15 melorheostosis patients found
      somatic mosaic activating MAP2K1 (MEK1) variants in eight, absent from unaffected
      bone and blood. Establishes the aetiology of sporadic melorheostosis as distinct
      from LEMD3.
- reference: PMID:26708699
  title: "Buschke-Ollendorff syndrome: a novel case series and systematic review."
  findings:
  - statement: >-
      Systematic review of 164 reported cases plus a Toronto cohort. Skin lesions 24%, bone
      lesions 20%, both 54%; family history 92%; short stature 7% and spinal stenosis 2%,
      both only in patients with osteopoikilosis; contested cognitive-delay association.
- reference: PMID:40195882
  title: "Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series."
  findings:
  - statement: >-
      Six LEMD3-variant probands with pooled literature analysis. Elastoma, collagenoma,
      mixed lesions and interstitial dermal mucin; post-incisional scarring in four of six;
      non-penetrant carrier parents; pelvis the commonest osteopoikilosis site.
- reference: PMID:32151766
  title: "Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants."
  findings:
  - statement: >-
      The only human bone-tissue study of BOS. Normal bone turnover markers and remodelling
      rate; sclerotic nodules of compact lamellar bone formed by modeling-based apposition
      with no woven bone, implicating bone lining cell activation.
- reference: PMID:1629625
  title: "Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture."
  findings:
  - statement: >-
      BOS skin fibroblasts produce 2-8 times normal tropoelastin with elevated elastin mRNA;
      apparently uninvolved skin is also elevated more than three-fold. The mechanistic
      basis for the cutaneous arm and for the focality problem.
- reference: PMID:19862465
  title: "The heterozygous Lemd3 +/GT mouse is not a murine model for osteopoikilosis in humans."
  findings:
  - statement: >-
      Radiography, quantitative micro-CT histomorphometry and histology of heterozygous
      Lemd3 gene-trap mice found no osteopoikilosis-like lesion and no structural
      difference from wild type. There is currently no animal model of the human bone
      phenotype.
- reference: PMID:15647271
  title: "The integral inner nuclear membrane protein MAN1 physically interacts with the R-Smad proteins to repress signaling by the transforming growth factor-beta superfamily of cytokines."
  findings:
  - statement: >-
      MAN1 binds R-SMADs but not SMAD4 at the inner nuclear membrane, ligand-independently,
      and inhibits R-SMAD phosphorylation, SMAD4 heterodimerisation, nuclear translocation
      and TGF-beta/BMP2/activin-responsive transcription.
- reference: PMID:30321401
  title: "Structural basis for receptor-regulated SMAD recognition by MAN1."
  findings:
  - statement: >-
      Crystal structures of SMAD1-MAN1 and SMAD2-MAN1 complexes; MAN1's C-terminal UHM
      domain and ULM form the surface that engages the R-SMAD MH2 domain and facilitates
      dephosphorylation.
- reference: PMID:30989250
  title: "Melorheostosis and Osteopoikilosis: A Review of Clinical Features and Pathogenesis."
  findings:
  - statement: >-
      Review of both entities and their molecular separation, with management guidance;
      melorheostosis affects fewer than 1 in a million and only about a third show the
      classic dripping-candle-wax pattern.
notes: >-
  **No treatment carries `target_mechanisms`, and that is a decision.** All six
  are symptomatic or diagnostic-sparing: reassurance and radiographic recognition
  to prevent an unnecessary oncological workup, genetic counselling and cascade
  evaluation, analgesia, excision of symptomatic connective tissue nevi,
  orthopaedic correction of established deformity, and bisphosphonates for
  symptomatic melorheostosis. None acts on LEMD3 dosage, on nuclear-envelope SMAD
  sequestration, or on BMP/TGF-beta output, so there is no mechanism node any of
  them could honestly be linked to. A `target_mechanisms` edge asserts that a
  treatment acts on a curated node, and drawing one from, say, analgesia to a
  bone-formation node would be false.

  Bisphosphonates are the case worth stating rather than passing over, because an
  antiresorptive plainly does act on bone and this entry does curate bone-formation
  nodes. The edge still would not be true. The nodes here are
  `Bone Lining Cell Activation and Modeling-Based Bone Formation` and the
  osteosclerotic-nodule and hyperostosis nodes downstream of it, which are
  modeling-based formation on quiescent surfaces; an antiresorptive acts on
  osteoclastic resorption, and the osteopoikilotic nodule has a normal remodelling
  rate to begin with. The drug is given for melorheostosis pain on admittedly weak
  evidence, which is a `target_phenotypes` claim and is recorded as one. Linking it
  to a formation node would assert a disease-modifying action nobody has shown.

  The absence is therefore a property of the therapeutic landscape for this disease,
  not an unfinished section; it should not be "completed" without a disease-modifying
  agent to hang on it. Note that this paragraph describes the entry's own structure,
  so it goes stale if a treatment is added and nothing gates it: check it against
  `treatments:` rather than trusting the count.

  **Relation to the other LEMD3 entries in this knowledge base.** A separate entry,
  `Dacryocystitis-Osteopoikilosis_Syndrome` (MONDO:0008158), covers a distinct MONDO
  concept in which recurrent dacryocystitis from nasolacrimal duct stenosis accompanies
  osteopoikilosis. That entry attributes its skeletal component to the same LEMD3
  mechanism modelled here, though LEMD3 has never been sequenced in the single reported
  pedigree. The two entries deliberately overlap on the osteopoikilosis pathophysiology
  and diverge on everything else; neither is a subtype of the other, and this entry does
  not model lacrimal or fibroproliferative manifestations.

  **No GeneReviews chapter exists.** PubMed and NCBI Bookshelf searches for
  GeneReviews coverage of Buschke-Ollendorff syndrome, osteopoikilosis, LEMD3 and
  melorheostosis all returned zero results (searched 2026-09-05). The mandatory
  GeneReviews phenotype baseline therefore could not be applied. The phenotype block was
  instead cross-checked against the largest available systematic review (PMID:26708699,
  164 cases) and the most recent genetically confirmed case series (PMID:40195882).

  **No mechanism module fits.** `kb/modules/` was searched for a conformance target.
  `fibrotic_response` is the closest candidate and is wrong: BOS connective tissue nevi
  are hamartomatous developmental overproduction of normal matrix, not a myofibroblast
  wound-healing programme, and there is no injury, no inflammatory phase and no
  contractile myofibroblast in the lesion. `aortopathy_tgfbeta_dysregulation` shares the
  TGF-beta axis but is scoped to the aortic wall.
  `defective_skeletal_mineralization` and `osteoporosis_bone_resorption` both run in the
  opposite direction. No `conforms_to` was declared rather than forcing one. A future
  "nuclear envelope SMAD termination failure" or "focal osteosclerosis" module would be
  the natural home.

  **Deep research provenance.** Two providers were run. `falcon` (Edison) produced a
  substantial, well-organised report that is the source of several framing points here,
  including the contiguous-12q14-deletion caveat and the ascertainment warning on the
  1-in-20,000 figure; it also mis-cited Mumm et al. 2007 as PMID:17223882 (that PMID is a
  different paper, Br J Dermatol, "Familial cutaneous collagenomas resulting from a novel
  mutation in LEMD3") and proposed two HP CURIEs that resolve to unrelated terms -
  HP:0005681 for "Osteopoikilosis" is in fact *Juvenile idiopathic arthritis*, and
  HP:0005781 for "Melorheostosis" is *Contractures of the large joints*. Neither was
  used; the bindings here (HP:0010739, HP:6000817) were verified against OLS. `asta`
  returned 20 papers of which none concerned this disease - the retrieval failed
  completely for this query - and nothing from it was used.

  **What is not curated here and why.** No `biochemical:` block: bone turnover markers
  and routine chemistry are normal in BOS and there is no biomarker. No `datasets:`
  block: no BOS-specific transcriptomic, proteomic or single-cell dataset was identified,
  in GEO or elsewhere. No `clinical_trials:` block: no interventional trial for BOS
  exists, and the melorheostosis MEK-inhibitor interest raised in PMID:29643386 concerns
  the MAP2K1-driven disease, not this one. No `environmental:` block: no exposure has
  any demonstrated role in a germline Mendelian disorder, and trauma prompting the
  radiograph that finds the lesion is ascertainment, not aetiology. No cognitive
  phenotype is curated, for the reasons in the "bos_cognitive_delay_association"
  discussion.

📚

References & Deep Research

References

11

PMID:15489854

Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis.

1 finding

Gene-discovery study. Heterozygous LEMD3 loss-of-function variants in osteopoikilosis and BOS families; LEMD3 interacts with BMP- and activin/TGF-beta-activated SMADs and antagonises both pathways in human cells. Its title also attributes melorheostosis to LEMD3, a claim later refuted for the sporadic form - see the "melorheostosis_attribution" discussion.

PMID:17087626

Deactivating germline mutations in LEMD3 cause osteopoikilosis and Buschke-Ollendorff syndrome, but not sporadic melorheostosis.

1 finding

Sequenced 11 individuals with sclerosing bone disorders. Germline LEMD3 mutations in OPK and BOS families including one with MEL-like lesions, and in none of the four with sporadic melorheostosis.

PMID:29643386

Somatic activating mutations in MAP2K1 cause melorheostosis.

1 finding

Paired affected/unaffected bone exome sequencing in 15 melorheostosis patients found somatic mosaic activating MAP2K1 (MEK1) variants in eight, absent from unaffected bone and blood. Establishes the aetiology of sporadic melorheostosis as distinct from LEMD3.

PMID:26708699

Buschke-Ollendorff syndrome: a novel case series and systematic review.

1 finding

Systematic review of 164 reported cases plus a Toronto cohort. Skin lesions 24%, bone lesions 20%, both 54%; family history 92%; short stature 7% and spinal stenosis 2%, both only in patients with osteopoikilosis; contested cognitive-delay association.

PMID:40195882

Clinical and Histopathological Characteristics of Buschke-Ollendorff Syndrome: A Case Series.

1 finding

Six LEMD3-variant probands with pooled literature analysis. Elastoma, collagenoma, mixed lesions and interstitial dermal mucin; post-incisional scarring in four of six; non-penetrant carrier parents; pelvis the commonest osteopoikilosis site.

PMID:32151766

Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants.

1 finding

The only human bone-tissue study of BOS. Normal bone turnover markers and remodelling rate; sclerotic nodules of compact lamellar bone formed by modeling-based apposition with no woven bone, implicating bone lining cell activation.

PMID:1629625

Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture.

1 finding

BOS skin fibroblasts produce 2-8 times normal tropoelastin with elevated elastin mRNA; apparently uninvolved skin is also elevated more than three-fold. The mechanistic basis for the cutaneous arm and for the focality problem.

PMID:19862465

The heterozygous Lemd3 +/GT mouse is not a murine model for osteopoikilosis in humans.

1 finding

Radiography, quantitative micro-CT histomorphometry and histology of heterozygous Lemd3 gene-trap mice found no osteopoikilosis-like lesion and no structural difference from wild type. There is currently no animal model of the human bone phenotype.

PMID:15647271

The integral inner nuclear membrane protein MAN1 physically interacts with the R-Smad proteins to repress signaling by the transforming growth factor-beta superfamily of cytokines.

1 finding

MAN1 binds R-SMADs but not SMAD4 at the inner nuclear membrane, ligand-independently, and inhibits R-SMAD phosphorylation, SMAD4 heterodimerisation, nuclear translocation and TGF-beta/BMP2/activin-responsive transcription.

PMID:30321401

Structural basis for receptor-regulated SMAD recognition by MAN1.

1 finding

Crystal structures of SMAD1-MAN1 and SMAD2-MAN1 complexes; MAN1's C-terminal UHM domain and ULM form the surface that engages the R-SMAD MH2 domain and facilitates dephosphorylation.

PMID:30989250

Melorheostosis and Osteopoikilosis: A Review of Clinical Features and Pathogenesis.

1 finding

Review of both entities and their molecular separation, with management guidance; melorheostosis affects fewer than 1 in a million and only about a third show the classic dripping-candle-wax pattern.

Deep Research

2

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Record notes

**No treatment carries `target_mechanisms`, and that is a decision.** All six are symptomatic or diagnostic-sparing: reassurance and radiographic recognition to prevent an unnecessary oncological workup, genetic counselling and cascade evaluation, analgesia, excision of symptomatic connective tissue nevi, orthopaedic correction of established deformity, and bisphosphonates for symptomatic melorheostosis. None acts on LEMD3 dosage, on nuclear-envelope SMAD sequestration, or on BMP/TGF-beta output, so there is no mechanism node any of them could honestly be linked to. A `target_mechanisms` edge asserts that a treatment acts on a curated node, and drawing one from, say, analgesia to a bone-formation node would be false. Bisphosphonates are the case worth stating rather than passing over, because an antiresorptive plainly does act on bone and this entry does curate bone-formation nodes. The edge still would not be true. The nodes here are `Bone Lining Cell Activation and Modeling-Based Bone Formation` and the osteosclerotic-nodule and hyperostosis nodes downstream of it, which are modeling-based formation on quiescent surfaces; an antiresorptive acts on osteoclastic resorption, and the osteopoikilotic nodule has a normal remodelling rate to begin with. The drug is given for melorheostosis pain on admittedly weak evidence, which is a `target_phenotypes` claim and is recorded as one. Linking it to a formation node would assert a disease-modifying action nobody has shown. The absence is therefore a property of the therapeutic landscape for this disease, not an unfinished section; it should not be "completed" without a disease-modifying agent to hang on it. Note that this paragraph describes the entry's own structure, so it goes stale if a treatment is added and nothing gates it: check it against `treatments:` rather than trusting the count. **Relation to the other LEMD3 entries in this knowledge base.** A separate entry, `Dacryocystitis-Osteopoikilosis_Syndrome` (MONDO:0008158), covers a distinct MONDO concept in which recurrent dacryocystitis from nasolacrimal duct stenosis accompanies osteopoikilosis. That entry attributes its skeletal component to the same LEMD3 mechanism modelled here, though LEMD3 has never been sequenced in the single reported pedigree. The two entries deliberately overlap on the osteopoikilosis pathophysiology and diverge on everything else; neither is a subtype of the other, and this entry does not model lacrimal or fibroproliferative manifestations. **No GeneReviews chapter exists.** PubMed and NCBI Bookshelf searches for GeneReviews coverage of Buschke-Ollendorff syndrome, osteopoikilosis, LEMD3 and melorheostosis all returned zero results (searched 2026-09-05). The mandatory GeneReviews phenotype baseline therefore could not be applied. The phenotype block was instead cross-checked against the largest available systematic review (PMID:26708699, 164 cases) and the most recent genetically confirmed case series (PMID:40195882). **No mechanism module fits.** `kb/modules/` was searched for a conformance target. `fibrotic_response` is the closest candidate and is wrong: BOS connective tissue nevi are hamartomatous developmental overproduction of normal matrix, not a myofibroblast wound-healing programme, and there is no injury, no inflammatory phase and no contractile myofibroblast in the lesion. `aortopathy_tgfbeta_dysregulation` shares the TGF-beta axis but is scoped to the aortic wall. `defective_skeletal_mineralization` and `osteoporosis_bone_resorption` both run in the opposite direction. No `conforms_to` was declared rather than forcing one. A future "nuclear envelope SMAD termination failure" or "focal osteosclerosis" module would be the natural home. **Deep research provenance.** Two providers were run. `falcon` (Edison) produced a substantial, well-organised report that is the source of several framing points here, including the contiguous-12q14-deletion caveat and the ascertainment warning on the 1-in-20,000 figure; it also mis-cited Mumm et al. 2007 as PMID:17223882 (that PMID is a different paper, Br J Dermatol, "Familial cutaneous collagenomas resulting from a novel mutation in LEMD3") and proposed two HP CURIEs that resolve to unrelated terms - HP:0005681 for "Osteopoikilosis" is in fact *Juvenile idiopathic arthritis*, and HP:0005781 for "Melorheostosis" is *Contractures of the large joints*. Neither was used; the bindings here (HP:0010739, HP:6000817) were verified against OLS. `asta` returned 20 papers of which none concerned this disease - the retrieval failed completely for this query - and nothing from it was used. **What is not curated here and why.** No `biochemical:` block: bone turnover markers and routine chemistry are normal in BOS and there is no biomarker. No `datasets:` block: no BOS-specific transcriptomic, proteomic or single-cell dataset was identified, in GEO or elsewhere. No `clinical_trials:` block: no interventional trial for BOS exists, and the melorheostosis MEK-inhibitor interest raised in PMID:29643386 concerns the MAP2K1-driven disease, not this one. No `environmental:` block: no exposure has any demonstrated role in a germline Mendelian disorder, and trauma prompting the radiograph that finds the lesion is ascertainment, not aetiology. No cognitive phenotype is curated, for the reasons in the "bos_cognitive_delay_association" discussion.

Create: Buschke-Ollendorff Syndrome · 2026-09-05T18:35:34Z · View source

Created kb/disorders/Buschke-Ollendorff_Syndrome.yaml (MONDO:0008157, LEMD3, hgnc:28887 verified against the committed hgnc cache and the schema's gene enum) from scratch. 2110 lines, 108 evidence snippets, all 108 verified against references_cache. Weighted compliance 89.3%. DEEP RESEARCH. Both requested providers ran to completion. - falcon (Edison Scientific), 524s, 18 citations, reference_validation 8/8 resolved, confabulation_rate 0.0. The report is genuinely good and several framing points in the entry come from it: the contiguous-12q14-deletion caveat, the warning that the 1-in-20,000 occurrence figure is not a registry measurement, the "no faithful animal model" summary, and the caution against treating cognitive delay as a syndrome feature. Two defects worth recording. (1) It cites Mumm et al. 2007 as PMID:17223882; that PMID is a different paper (Br J Dermatol, "Familial cutaneous collagenomas resulting from a novel mutation in LEMD3"). The correct Mumm PMID is 17087626, which is what this entry uses. The mis-cited PMID turned out to be a real and relevant paper, but its PubMed record has no retrievable abstract (content_type: unavailable), so it could not be cited with a snippet and was dropped. (2) Its term_validation block reported only one mislabelled term (the MONDO id, trivially), but two of the HP CURIEs it proposed in prose tables resolve to unrelated concepts: HP:0005681 offered as "Osteopoikilosis" is actually Juvenile idiopathic arthritis, and HP:0005781 offered as "Melorheostosis" is actually Contractures of the large joints. Neither was used. Every HP/GO/CL/UBERON/NCIT binding in this entry was checked independently against the committed caches or the OLS REST API before use; the correct bindings are HP:0010739 and HP:6000817. - asta, 6.7s, 20 papers. The retrieval failed completely for this query: not one returned paper concerns Buschke-Ollendorff syndrome, osteopoikilosis, LEMD3 or melorheostosis (they are about Hutchinson-Gilford progeria, Bartter syndrome, epidermolysis bullosa, Bardet-Biedl, pulmonary hypertension and so on). Its reference_validation is clean because the papers exist, not because they are relevant - a good illustration of why "36/36 resolved" is not an on-topic guarantee. Nothing from the asta report was used. Because asta contributed nothing, the reference set was built primarily from a systematic PubMed E-utilities sweep (Buschke-Ollendorff; LEMD3; osteopoikilosis AND (LEMD3 OR MAN1); melorheostosis AND MAP2K1; MAN1 AND Smad; LEMD3 AND mouse; connective tissue nevus histopathology) plus the reference lists of the two review articles. GENEREVIEWS. There is no GeneReviews chapter. PubMed searches for "<term> GeneReviews[All Fields]" over Buschke-Ollendorff, osteopoikilosis, LEMD3 and melorheostosis all returned 0 hits, as did NCBI Bookshelf queries. The mandatory baseline therefore could not be applied and this is recorded in the entry's notes. In its place the phenotype block was cross-checked against the largest systematic review (PMID:26708699, 164 cases) and the most recent genetically confirmed series (PMID:40195882). MECHANISM MODEL. Nine pathophysiology nodes forming a branching chain with bare-name downstream targets: LEMD3 Haploinsufficiency (MOLECULAR) -> Loss of Nuclear Envelope R-SMAD Antagonism (MOLECULAR) -> two parallel arms, Increased BMP-SMAD1/5/8 Transcriptional Output and Increased TGF-beta-SMAD2/3 Transcriptional Output (both MOLECULAR) -> Bone Lining Cell Activation and Modeling-Based Bone Formation (CELLULAR) and Dermal Fibroblast Elastin and Collagen Overproduction (CELLULAR) -> Focal Trabecular Osteosclerotic Nodule Formation, Segmental Cortical Hyperostosis and Dermal Connective Tissue Nevus Formation (all TISSUE) -> the phenotype nodes. Both arms feed the bone branch, because TGF-beta acts on the osteoblast lineage too and no study separates the two contributions in human tissue. mechanism_confidence is deliberately graded down the chain: ESTABLISHED for the molecular interaction (structural, biochemical and orthologue evidence), PROVISIONAL for the two transcriptional-output nodes (never measured in patient bone or skin), ESTABLISHED again for the bone tissue lesion (human histomorphometry, PMID:32151766) and the fibroblast overproduction (PMID:1629625), and HYPOTHETICAL for Segmental Cortical Hyperostosis. The two edges into Bone Lining Cell Activation are INDIRECT_UNKNOWN_INTERMEDIATES rather than DIRECT for the same reason. MELORHEOSTOSIS ATTRIBUTION. Handled as a first-class CONTROVERSY discussion (discussion_id: melorheostosis_attribution) rather than being decided in prose, because the honest position has three parts that pull in different directions. (i) The 2004 gene-discovery paper (PMID:15489854) put melorheostosis in its title; that general claim is refuted, and the discussion carries two REFUTE evidence items against it - PMID:17087626 "no LEMD3 mutation was found for any other patient, including all four with sporadic MEL" and PMID:19438932's independent replication. Those are, as far as I can tell, the correct use of supports: REFUTE here: the quoted sentences contradict the proposition rather than merely failing to support it. (ii) Sporadic isolated melorheostosis is a somatic MAP2K1 mosaic disease (PMID:29643386), and it is modelled as a differential_diagnosis, not as part of this entry's pathograph. (iii) The LEMD3-associated segmental lesion is real but unexplained: everyone in the kindred carries the allele and only one member develops the lesion, and the postulated somatic second hit at LEMD3 has been searched for and not found (PMID:15489854, PMID:16470551). So the entry keeps a Segmental Cortical Hyperostosis node with mechanism_confidence HYPOTHETICAL, a "BOS with Melorheostosis" subtype, and an explicit statement in the node description that it makes no claim about sporadic melorheostosis. This seemed better than either asserting LEMD3 causation or deleting the lesion from an entry in which it genuinely occurs. OTHER MODELLING DECISIONS A REVIEWER SHOULD KNOW. - has_subtypes are presentation-defined intrafamilial forms (Complete, Skin-Limited, Bone-Limited, BOS with Melorheostosis), quantified by PMID:26708699's 24/20/54 split. I deliberately did NOT make "isolated osteopoikilosis" a subtype in the ontological sense: MONDO places MONDO:0015634 under osteopoikilosis, not under BOS, and BOS is defined by having both components. The MONDO binding on Bone-Limited BOS is labelled in its description as a cross-reference to the concept, not a subsumption claim. - animal_models carries three entries. The headline one is the heterozygous Lemd3+/GT mouse (PMID:19862465), linked FAILS_TO_RECAPITULATE against the bone-lesion node with fidelity LOW, model_scale TISSUE (equal to target scale, so no extrapolation), two readouts, both limitations and evidence as the schema requires for a negative link, and typed divergences (SPECIES_MISMATCH INVALIDATING, BOUNDARY_OMISSION QUALIFYING - the study never looked at skin). A matching HUMAN_MODEL_MISMATCH discussion (bos_no_animal_model) sets out the three alternative explanations and proposes an osteoblast-lineage conditional experiment. The Man1 Smad-domain-deletion mouse (PMID:16943282) and the Xenopus XMAN1 system (PMID:12642484) are linked to the molecular nodes with PARTIALLY_RECAPITULATES and PERTURBS respectively. - No conforms_to. kb/modules/ was searched. fibrotic_response is the near miss and is wrong - a connective tissue nevus is hamartomatous developmental matrix overproduction, not a myofibroblast wound-healing programme, with no injury, no inflammatory phase and no myofibroblast. aortopathy_tgfbeta_dysregulation shares the axis but is aorta-scoped; defective_skeletal_mineralization and osteoporosis_bone_resorption run the other way. Reasoning recorded in the entry's notes rather than forcing a target. - Two histopathology findings (dermal elastoma, dermal collagenoma) and one imaging finding carry a free-text preferred_term with no term:, because no NCIT HistopathologyFindingTerm (reachable from NCIT:C83490) and no HP descendant of HP:0025461 names them. HP:0025164/HP:6000022 are bound in the phenotypes block instead, where the enum root (HP:0000118) does admit them. The bone nodule is bound to the generic NCIT:C69309 Sclerosis, whose reachability from NCIT:C83490 I checked via OLS. - Empty by decision, with reasons in notes: biochemical (turnover markers are normal, no biomarker exists), datasets (no BOS-specific omics dataset was found), clinical_trials (none exist; the MEK-inhibitor interest belongs to MAP2K1 melorheostosis), environmental (germline Mendelian; trauma prompting the diagnostic radiograph is ascertainment, not aetiology). No cognitive phenotype was curated - PMID:26708699's cognitive-delay signal appears only in cases published from 2007 onwards, which is what reporting bias plus the arrival of microarray-detected 12q14 deletions looks like; recorded as an OPEN_QUESTION discussion instead. - prevalence measure_type is UNKNOWN, not ANNUAL_INCIDENCE, even though the source says "estimated incidence": no denominator population and no observation period are given. rate_per_100000 5.0, prevalence_class BAND_1_9_PER_100000. - Cross-referenced kb/disorders/Dacryocystitis-Osteopoikilosis_Syndrome.yaml (MONDO:0008158, also LEMD3) in notes. That file was read but not edited. REFERENCES CONSIDERED AND NOT USED. PMID:17223882 (familial cutaneous collagenomas from a novel LEMD3 mutation) and PMID:27115577 and PMID:12664025 and PMID:34511237 - all four have content_type unavailable or empty in the cache, so no exact quote can be taken from them. PMID:30989250's full text is a line-wrapped PDF; only its abstract paragraph was quoted. VALIDATION ACTUALLY RUN AND READ, on the final tree. - just validate kb/disorders/Buschke-Ollendorff_Syndrome.yaml (under flock): schema "No issues found"; terms "Validation passed"; references "All validations passed", 108/108 snippets verified. Caches unchanged, so normalize-cache was skipped. - just count-verified-snippets: 108/108 verified against cached references. - just check-entity-refs: OK, entity references resolve. - just check-causal-targets: OK, no new broken pathograph targets. - just check-duplicate-keys: OK, no duplicate mapping keys. - just check-qualifier-terms: OK (this entry uses no qualifiers). - just check-enum-values: OK, no out-of-enum values. - just compliance: Weighted Compliance 89.3%. - Whole-KB gates check-folded-hyphens, check-title-snippets, check-snippet-grading and check-environmental-evidence all pass. check-snippet-length fails on the shared tree, but on three snippets in Chylomicron_Retention_Disease.yaml and Sotos_Syndrome.yaml belonging to other concurrent curation work, not on this entry. Not run, deliberately: whole-KB sweeps (just qc, validate-all, normalize-cache) and just validate-disorders, which the orchestrator batches; six other agents share this checkout. No git command was run.

Asta ▸

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Buschke-Ollendorff Syndrome. Core disease mechanisms, molecular and cellul...

Asta Scientific Corpus Retrieval 20 citations 2026-09-05T17:58:40.057110

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Buschke-Ollendorff Syndrome. Core disease mechanisms, molecular and cellul...

This report is retrieval-only and is generated directly from Asta results.

Papers retrieved: 20
Snippets retrieved: 20

Relevant Papers

[1] Transcriptional profiling of Hutchinson-Gilford progeria patients identifies primary target pathways of progerin

Authors: Sandra Vidak, Sohyoung Kim, Tom Misteli
Year: 2026
Venue: Nucleus
URL: https://www.semanticscholar.org/paper/4bd99b0875508364d8672b6da5a50d024d485a53
DOI: 10.1080/19491034.2025.2611484
PMID: 41489464
PMCID: 12773485
Citations: 1
Summary: To probe the clinical relevance of previously implicated cellular pathways and to address the extent of gene expression heterogeneity between patients, transcriptomic analysis of a comprehensive set of HGPS patients finds misexpression of several cellular pathways, including multiple signaling pathways, the UPR and mesodermal cell fate specification.
Evidence snippets:
Snippet 1 (score: 0.393) > Oxidative stress represents another key pathogenic mechanism in HGPS, as impaired NRF2 activity or increased reactive oxygen species (ROS) levels are sufficient to recapitulate HGPSassociated phenotypes [17,32,60]. Collectively, these findings underscore the multifactorial nature of HGPS pathogenesis, implicating interconnected signaling cascades involved in inflammation, oxidative stress, proteostasis, and vascular remodeling. Reassuringly, our findings indicate that many of the major pathways that have been described to contribute to HGPS phenotypes in mouse and cellular disease models are also misregulated in progeria patients, and targeting these pathways may provide therapeutic avenues to mitigate disease severity and improve outcomes in HGPS. > Although individuals with HGPS typically exhibit a characteristic set of clinical features, such as craniofacial abnormalities, growth retardation, and cardiovascular complications, there is notable variability in the age of onset, severity, and progression of symptoms between patients [7,9]. At the cellular level, HGPS is associated with several hallmark abnormalities, including nuclear envelope defects, decreased expression of several nuclear proteins and epigenetic marks, mitochondrial dysfunction, and increased cellular senescence [1,11,30,31,61]. These cellular phenotypes also exhibit considerable variation between patients, possibly contributing to differences in clinical outcomes. Our results indicate that even though some degree of transcriptional heterogeneity between the individual patients exists, the majority of patients exhibit misregulation of a set of shared pathways, suggesting that these pathways are universal driver mechanisms in HGPS. Further work is needed to understand the molecular and genetic factors that underlie inter-individual variability in disease expression and progression. > A limitation of pathway analysis of HGPS patient samples is to distinguish the pathways which are directly targeted by the disease-causing progerin protein and the emergence of adaptive secondary response pathways during progression of the disease in patients during their lifetime. The same caveat applies to the use of cell-based models used in the study of HGPS disease mechanisms.

[2] New therapeutic targets in rare genetic skeletal diseases

Authors: M. Briggs, Peter A. Bell, M. Wright, K. A. Pirog
Year: 2015
Venue: Expert Opinion on Orphan Drugs
URL: https://www.semanticscholar.org/paper/1363107f71ae6d2d60abca471cddf3da5d13644b
DOI: 10.1517/21678707.2015.1083853
PMID: 26635999
PMCID: 4643203
Citations: 39
Influential citations: 1
Summary: An overview of disease mechanisms that are shared amongst groups of different GSDs and potential therapeutic approaches that are under investigation are described to generate critical mass for the identification and validation of novel therapeutic targets and biomarkers.
Evidence snippets:
Snippet 1 (score: 0.390) > However, emerging knowledge suggests that the primary genetic defect may be less important than the cells' response to the expression of the mutant gene product [107]. Moreover, the largely overlooked response of a cell (i.e. chondrocyte) to the abnormal extracellular environment is also important for disease progression as illustrated by several GSDs discussed in this review. > It is important that 'omics'-based approaches and technologies are systematically applied to the study of rare GSDs so that definitive reference profiles and disease signatures are generated for each phenotype. These can then be used in a Systems Biology approach to identify both common and dissimilar pathological signatures and disease mechanisms. This approach is entirely dependent upon relevant in vitro and in vivo models (and also novel 'disease-mechanism phenocopies' [107]) for testing new diagnostic and prognostic tools and for determining the molecular mechanisms that underpin the pathophysiology so that effective therapeutic treatments can be developed and validated. This approach will eventually lead to personalized treatments and care strategies centred on shared disease mechanisms with the use of relevant biomarkers to monitor the efficacy of treatment and disease progression. > It is vital that all relevant stakeholders are involved from the outset in defining the appropriate outcomes of any potential therapeutic regime. The perceptions of a successful therapy can differ widely between the clinical academic community and the relevant patient-support groups and it is vital that there is engagement on all these issues. > In summary, the identification of causative genes and mutations for GSDs over the last 20 years, coupled with the generation and in-depth analysis of a plethora of relevant cell and mouse models, has derived new knowledge on disease mechanisms and suggested potential therapeutic targets. The fast-evolving hypothesis that clinically disparate diseases can share common disease mechanisms is a powerful concept that will generate critical mass for the identification and validation of novel therapeutic targets and biomarkers.

[3] Molecular Genetics of Bartter Syndrome: Bridging Genotype–Phenotype Correlations and Precision Therapeutics

Authors: Lina Zhu, Yang Li, Yiyao Bao
Year: 2026
Venue: Current Issues in Molecular Biology
URL: https://www.semanticscholar.org/paper/a5e1ddccfa7d333834c4d32be123c71bfd573f83
DOI: 10.3390/cimb48040422
PMID: 42042082
PMCID: 13114623
Summary: A comprehensive framework to provide a comprehensive framework to facilitate precise diagnosis and individualized treatment strategies, ultimately advancing precision medicine in the management of Bartter syndrome is provided.
Evidence snippets:
Snippet 1 (score: 0.387) > Molecular genetic research on Bartter syndrome has made remarkable strides, elucidating the principal BS genes SLC12A1, KCNJ1, CLCNKB, BSND, and MAGED2 and their corresponding protein defects, thereby refining the molecular framework of disease classification while separating CaSR-associated Bartter-like disease from the core canonical BS spectrum. This progress has significantly deepened our understanding of the underlying pathophysiology and provided an essential framework for correlating genotypes with clinical phenotypes. However, the intricate relationship between genetic mutations and clinical manifestations remains complex and multifaceted, reflecting the profound heterogeneity of the syndrome. Addressing these diagnostic challenges and refining disease classification beyond traditional clinical criteria requires an integrative approach that seamlessly balances high-throughput sequencing technologies with rigorous functional studies. > The mechanisms by which these genetic mutations lead to protein dysfunction are diverse, encompassing critical defects in protein expression, impaired membrane localization, and direct functional impairments. Notably, aberrant protein folding, endoplasmic reticulum-associated degradation (ERAD), and splicing abnormalities have emerged as critical pathogenic pathways. These mechanistic insights not only enhance our fundamental understanding of the disease but also highlight highly promising therapeutic targets. While current treatments remain predominantly symptomatic, focusing primarily on managing electrolyte imbalances and associated complications, they inherently fail to address the underlying molecular defects driving the disease. > The precise identification of specific molecular defects opens innovative avenues for the development of targeted interventions aimed at correcting or compensating for specific protein abnormalities. For instance, molecular chaperones that assist in protein folding, agents that modulate aberrant splicing, and future gene-based strategies represent important experimental directions for mechanism-based therapy. Consequently, the future of Bartter syndrome management may increasingly move toward precision medicine tailored to the molecular pathology of individual patients. However, the transition from concept to clinical implementation will require substantial additional functional, translational, and trial-level evidence. Such mechanism-based strategies promise not only to alleviate clinical symptoms but to fundamentally modify disease progression, thereby drastically improving long-term prognosis and quality of life for patients.

[4] Tubular Aggregate Myopathies: Genetic Heterogeneity and Diverse Clinical Features Converging on Calcium Dysregulation

Authors: Matteo Serano, F. Fiore, Vincenzo Sorrentino, Daniela Rossi
Year: 2026
Venue: Cells
URL: https://www.semanticscholar.org/paper/c53accfaacb913a69aeeb832222593ca90afabeb
DOI: 10.3390/cells15070635
PMID: 41972723
PMCID: 13072200
Citations: 2
Summary: Highlights TAM is an inherited muscle disorder caused by STIM1 and ORAI1 mutations that disrupt calcium entry, leading to tubular aggregates and muscle dysfunction. Its overlap with Stormorken syndrome suggests a disease continuum. Although the genetics are known, mechanisms behind aggregate formation and multisystem features remain unclear, highlighting the need for deeper insight and targeted therapies. What are the main findings? Genetics and Pathogenesis: Tubular aggregate myopathy (TAM)...
Evidence snippets:
Snippet 1 (score: 0.380) > , hypocalcemia, hyposplenism, and ichthyosis, thereby resulting in a clinical picture that overlaps with symptoms of Stormorken (STRMK) syndrome. Considerable heterogeneity exists in age of onset, severity, and extra-muscular involvement, suggesting that TAM and STRMK represent a continuum rather than distinct entities. Histopathological hallmarks include TAs staining positive for SR proteins and displaying a honeycomb-like ultrastructure, consistent with aberrant SR remodeling. Mutations in genes encoding key regulators of store-operated calcium entry (SOCE), including STIM1 and ORAI1 have been identified as major contributors to TAM and its broader clinical spectrum, which encompasses STRMK syndrome, whereas mutations in CASQ1 and RYR1, have been described in only a minority of patients. Despite advances in delineating the genetic and molecular basis of TAM, key questions remain regarding the mechanisms that drive TAs formation and translate Ca2+ dysregulation into muscle dysfunction and multisystem disease. Understanding the molecular mechanisms underlying TAM and STRMK syndrome is crucial for developing targeted therapies. Moreover, further research is needed to elucidate additional pathways involved in disease progression and to refine genotype–phenotype correlations. This review summarizes current knowledge on the genetics, pathophysiology, clinical features, and diagnostic hallmarks of TAM, with particular emphasis on the role of Ca2+ homeostasis.

[5] Ellis–van Creveld syndrome with facial dysmorphic features in an Egyptian child

Authors: R. Shawky, D. I. Sadik, N. Seifeldin
Year: 2010
Venue: Egyptian Journal of Medical Human Genetics
URL: https://www.semanticscholar.org/paper/fb61ac8ae2dfea28141342fc3fb585d728f37b0d
DOI: 10.1016/J.EJMHG.2010.05.001
Citations: 6
Summary: A patient with the typical features of the syndrome but with facial dysmorphic features (upward slant of eyes, megalocornea and high forehead), for the first time in the literature are reported.
Evidence snippets:
Snippet 1 (score: 0.378) > [11][12][13]. Disruption of either of these non-homologous genes results in an indistinguishable heart-hand phenotype, but the role of EVC and LBN in development and disease pathogenesis remains largely unknown. > However, EvC syndrome is considered part of an emerging class of diseases called ciliopathies. The underlying cause may be a dysfunctional molecular mechanism in the primary cilia structures of the cell, organelles which are present in many cellular types throughout the human body. The cilia defects adversely affect ''numerous critical developmental signaling pathways'' essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases. Known ciliopathies include primary ciliary dyskinesia, Bardet-Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alstrom syndrome, Meckel-Gruber syndrome and some forms of retinal degeneration [14]. > We present here a clinical analysis of a male child manifesting many of the specific features of EvC, but with facial dysmorphic features for the first time in the literature.

[6] Molecular genetic basis of epidermolysis bullosa

Authors: Y. Kotalevskaya, V. Stepanov
Year: 2023
Venue: Vavilov Journal of Genetics and Breeding
URL: https://www.semanticscholar.org/paper/720cbefbd0435504a6ed670ccf4f491dfbd3f143
DOI: 10.18699/VJGB-23-04
PMID: 36923479
PMCID: 10009482
Citations: 9
Influential citations: 3
Summary: The study of clinical, genetic and ultrastructural changes in EB has significantly expanded the understanding of the natural history of the disease and supplemented the data on genotype-phenotype correlations, promotes the search and study of epigenetic and non-genetic disease modifier factors, and also allows developing approaches to radical treatment of the Disease.
Evidence snippets:
Snippet 1 (score: 0.374) > Epidermolysis bullosa (EB) is an inherited disorder of skin fragility, caused by mutations in a large number of genes associated with skin integrity and dermal-epidermal adhesion. Skin fragility is manifested by a decrease in resistance to external mechanical influences, the clinical signs of which are the formation of blisters, erosions and wounds on the skin and mucous membranes. EB is a multisystemic disease and characterized by a wide phenotypic spectrum with extracutaneous complications in severe types, besides the skin and mucous membranes, with high mortality. More than 30 clinical subtypes have been identified, which are grouped into four main types: simplex EB, junctional EB, dystrophic EB and Kindler syndrome. To date, pathogenic variants in 16 different genes are associated with EB and encode proteins that are part of the skin anchoring structures or are signaling proteins. Genetic mutations cause dysfunction of cellular structures, differentiation, proliferation and apoptosis of cells, leading to mechanical instability of the skin. The formation of reduced proteins or decrease in their level leads mainly to functional disorders, forming mild or intermediate severe phenotypes. Absent protein expression is a result of null genetic variants and leads to structural abnormalities, causing a severe clinical phenotype. For most of the genes involved in the pathogenesis of EB, certain relationships have been established between the type and position of genetic variant and the severity of the clinical manifestations of the disease. Establishing an accurate diagnosis depends on the correlation of clinical, genealogical and immunohistological data in combination with molecular genetic testing. In general, the study of clinical, genetic and ultrastructural changes in EB has significantly expanded the understanding of the natural history of the disease and supplemented the data on genotype-phenotype correlations, promotes the search and study of epigenetic and non-genetic disease modifier factors, and also allows developing approaches to radical treatment of the disease. New advances of sequencing technologies have made it possible to describe new phenotypes and study their genetic and molecular mechanisms. This article describes the pathogenetic aspects and genes that cause main and rare syndromic subtypes of EB.

[7] Improving Drug Trial Success Rates in Systemic Lupus Erythematosus: Endotyping-based Patient Stratification Could be the way Forward

Authors: Anand N. Malaviya, Neeraj Jain
Year: 2024
Venue: Indian Journal of Rheumatology
URL: https://www.semanticscholar.org/paper/d023e00e1b518c7089cb3d310e78b3b6cb5bd895
DOI: 10.1177/09733698241229780
Summary: Using a 2-pronged approach of defining theratypes of pre-endotyped patients could fast-track drug discovery of drugs for SLE treatment and pave the way for more effective treatments for SLE.
Evidence snippets:
Snippet 1 (score: 0.373) > Over the years, it has been observed that the different phenotypes do not offer insight into the underlying pathobiological mechanism; these may or may not have the same underlying abnormalities in disease-causing biological pathways.For an appropriate understanding of that, a much deeper analysis of the biological mechanisms involved in causing the pathobiology, is required.The evolving understanding of the physiology of the biological systems has discovered a variety of biochemical, metabolic, inflammatory, immunological cells and subcellular milieu that can be exploited to understand their role in health and disease.Studying the heterogeneity in type-1 diabetes, it was demonstrated that traits are often linked (e.g., age and HLA-specific autoimmunity) in such a thrombocytopaenia and/or leukopenia/ lymphopenia, Evan's syndrome, often associated with antiphospholipid syndrome).5. 'Thromboembolic lupus' associated with anti-phospholipid syndrome (APS).6. 'Obstetric complications of lupus' (usually with recurrent pregnancy loss associated with secondary anti-phospholipid syndrome).7. Others-uncommon presentations (recalcitrant dermatological manifestations, others).way that suggests associations, which could be built into distinct pathobiological entities. 33Using molecular and omics techniques, these abnormalities can be characterised with high precision.Using these techniques, a particular clinically diagnosable disease, especially those with protean manifestations, can be further categorised in clearly defined subsets.This approach of precisely subtyping such diseases is called 'Endotyping' 33,34 that further stratifies any clinical disease into different 'endotypes'.As endotypes characterise the disease at subcellular/biochemical/molecular level, it becomes possible to correct that abnormality with targeted treatment.The current popular term for such a treatment approach is called 'precision medicine'.

[8] Changes in Serum Proteomic Profiles at Different Stages of Pregnancy Toxemia in Goats

Authors: M. Uzti̇mür, C. N. Ünal, Gurler Akpinar
Year: 2025
Venue: Journal of Veterinary Internal Medicine
URL: https://www.semanticscholar.org/paper/4b9c488b5dbd65d7b26fd2ad9aed70e8c4b59942
DOI: 10.1111/jvim.70139
PMID: 40492724
PMCID: 12150350
Citations: 2
Summary: Understanding the serum proteome profiles of goats with pregnancy toxemia might help identify the proteomes and pathways responsible for the development of this disease and improve diagnosis and treatment.
Evidence snippets:
Snippet 1 (score: 0.372) > The pathophysiology and progression of this disease are not fully understood. > Traditional biomedical research has focused on the analysis of single genes, proteins, metabolites, or metabolic pathways in diseases. This molecular reductionist approach is based on the assumption that identifying genetic variations and molecular components will lead to new treatments for diseases [13][14][15][16]. However, many diseases are complex and multifactorial, and in order to determine the phenotype of such diseases, it is necessary to understand the changes that occur in more than one gene, pathway, protein, or metabolite at the cellular, tissue, and organismal levels [17][18][19]. Therefore, in recent years, proteomics, as one field of multi-omics technologies, has helped in evaluating the complex pathogenetic mechanisms of different diseases from a broad perspective and has made substantial contributions [20,21]. In veterinary medicine, proteomic analysis of metabolic diseases such as ketosis [16], hypocalcemia [22], and fatty liver [23] in dairy cows has contributed valuable insights for the definition of new pathophysiological pathways and new diagnosis and treatment protocols for these diseases. The proteomic approach can contribute importantly to a broad and detailed understanding of the changes that occur at the organismal level associated with the increase in BHBA concentration in goats with pregnancy toxemia. Our aim was to evaluate the serum protein profiles of goats with SPT or CPT using proteomic techniques to determine the proteomic profiles of these animals and to identify the relevant pathophysiological mechanisms.

[9] Diagnostic and referral pathways in patients with rare lipodystrophy and insulin-resistance syndromes: key milestones assessed from a national reference center

Authors: B. Donadille, S. Janmaat, H. Mosbah, Inès Belalem, Sophie Lamothe et al.
Year: 2024
Venue: Orphanet Journal of Rare Diseases
URL: https://www.semanticscholar.org/paper/823da349ccd35ba745c9241586d2fa0cb443118a
DOI: 10.1186/s13023-024-03173-2
PMID: 38678257
PMCID: 11056061
Citations: 5
Summary: The national rare disease database provides an important tool for assessment of care pathways in patients with lipodystrophy and rare insulin-resistance syndromes in France and improving knowledge to reduce diagnostic delay is an important objective of the PRISIS reference center.
Evidence snippets:
Snippet 1 (score: 0.371) > Lipodystrophy syndromes are heterogeneous chronic rare diseases, characterized by anatomical and functional defects of adipose tissue resulting from genetic or acquired causes. Lipodystrophy syndromes present as systemic diseases with progressive metabolic alterations associated with insulin-resistance, such as diabetes, hypertriglyceridemia, non-alcoholic fatty liver disease, and ovarian dysfunction in women, with multi-tissue involvement depending on the underlying cause. Besides different clinical presentations with generalized or partial lipoatrophy, with or without fat overgrowth in body areas without lipoatrophy, these syndromes are highly heterogeneous diseases. The onset of lipodystrophy may be precocious, from birth or early infancy, or delayed in late childhood or adulthood. Some subtypes of lipodystrophy are associated with specific clinical signs and complications, such as cardiovascular and/or neurological involvement [1][2][3]. Acquired forms of lipodystrophies generally result from autoimmune mechanisms and/or iatrogenic therapies. The identification of causative pathogenic variants in more than 20 genes leading to monogenic forms of lipodystrophies has highlighted several determinants in adipose tissue pathophysiology. Molecular and cellular bases of monogenic lipodystrophy syndromes involve, among others, altered adipocyte differentiation, structure and/or regulation of the adipocyte lipid droplet and/ or premature cellular senescence. This field of research, still highly productive, indicates adipose tissue as a major actor to ensure proper whole-body insulin sensitivity [4]. Other rare conditions characterized by severe insulinresistance without primary adipose tissue dysfunction result from direct defects in insulin signaling pathways, due to specific genetic or dysimmune disorders [5]. The four main forms of Congenital Generalized Lipodystrophy, referred to as CGL1 to CGL4, are due to pathogenic variants in AGPAT2, BSCL2, CAV1, and CAVIN1/PTRF genes, respectively.

[10] Modelling Mitochondrial Disease in Human Pluripotent Stem Cells: What Have We Learned?

Authors: Cameron L. McKnight, Y. C. Low, D. Elliott, D. Thorburn, A. E. Frazier
Year: 2021
Venue: International Journal of Molecular Sciences
URL: https://www.semanticscholar.org/paper/bf41f9d980522896fcd2284bd630fbb418e55941
DOI: 10.3390/ijms22147730
PMID: 34299348
PMCID: 8306397
Citations: 21
Summary: Mitochondrial diseases disrupt cellular energy production and are among the most complex group of inherited genetic disorders. Affecting approximately 1 in 5000 live births, they are both clinically and genetically heterogeneous, and can be highly tissue specific, but most often affect cell types with high energy demands in the brain, heart, and kidneys. There are currently no clinically validated treatment options available, despite several agents showing therapeutic promise. However, modell...
Evidence snippets:
Snippet 1 (score: 0.370) > Mitochondrial disease hPSC models provide a system to study disease gene-or mutation-related pathomechanisms in tissues relevant to the clinical phenotype. Ultimately, the long-term goal of these models would be to identify a phenotype in a clinically relevant cell type that could be used to validate efficacy of targeted treatments, or for use in highthroughput treatment trials [94][95][96] (Figure 2). > There are now a wide range of endpoints that have been validated in terminally differentiated cell types to investigate the underlying cellular mechanisms of disease and efficiently identify targetable pathways. Many of these approaches can also be adapted to suit different cell types and even organoids at scale. The tissue specific nature of mitochondrial diseases means that mitochondrial function post-differentiation can be distinct to that from the undifferentiated stem cells or original fibroblast line, often greatly exaggerating any underlying defects [97]. Additionally, detailed transcriptomic and proteomic analyses can elucidate cellular compensation mechanisms and potential target pathways to inform downstream treatment studies [98,99]. Other approaches include microscopic visualization of key cellular features to determine a mutation's impact on cell structure or function [100]. For cardiomyocytes and neurons, electrophysiology can provide highly sensitive data to identify even subtle functional changes [101]. Calcium imaging can be particularly informative in the context of mitochondrial diseases, since calcium handling is a key role of mitochondria [102,103].

[11] Molecular mechanisms and phenotypic diversity in Bardet-Biedl syndrome

Authors: Carlos Lopez Solarat
Year: Unknown
Venue: Unknown venue
URL: https://www.semanticscholar.org/paper/a574e514383f0a43ed35aa91418e699308c97629
DOI: 10.35869/11093/8876
Summary: This thesis primarily aims to identify and elucidate common and fundamental cellular metabolic mechanisms that could account for the considerable phenotypic diversity observed in BBS.
Evidence snippets:
Snippet 1 (score: 0.368) > Ciliopathies are a group of rare diseases characterized by a wrong function or structure of the cilia. One of them is Bardet-Biedl syndrome, a multisystemic disease whose main symptoms are retinal degeneration, obesity, polydactyly, cognitive impairment, cryptorchidism and wrong renal structure and function, as well as other less common but of great clinical relevance symptoms such as liver fibrosis, diabetes and hypertension. Ciliopathies are a group of diseases characterized by an alteration in the function or structure of the primary cilium, a cellular organelle responsible for signal transduction. One of these diseases is Bardet-Biedl syndrome (BBS MIM # 209900), which is characterized by mutations in genes that code for a series of proteins that interact to form a protein complex, the BBSome. The precise molecular process underlying BBS manifestation remains unclear. The positioning and involvement of BBSome in ciliary signal transduction suggest a specific disruption of particular metabolic pathways. Nevertheless, the extensive phenotypic variability in this syndrome coincides with distinct tissue alterations, indicating that BBSome likely affects cell signalling through a shared mechanism influencing a majority of receptors within the cell. Numerous ciliopathies exhibit a pathological phenotype that significantly overlaps not only with other ciliopathies but also with different disease types. This is exemplified by BBS and mitochondrial diseases, where both entail multiple tissues and present symptoms such as optic atrophy, neurological involvement, and metabolic irregularities. Consequently, mitochondrial dysfunction could be viewed as a potential novel mechanism contributing to specific BBS symptoms. Building upon the aforementioned points, this thesis primarily aims to identify and elucidate common and fundamental cellular metabolic mechanisms that could account for the considerable phenotypic diversity observed in BBS.

[12] Investigating the Transition of Pre-Symptomatic to Symptomatic Huntington’s Disease Status Based on Omics Data

Authors: Christiana C. Christodoulou, M. Zachariou, M. Tomazou, E. Karatzas, C. Demetriou et al.
Year: 2020
Venue: International Journal of Molecular Sciences
URL: https://www.semanticscholar.org/paper/04a48e68a0a0ad9eca22aeffdb8c22c7fb41ed86
DOI: 10.3390/ijms21197414
PMID: 33049985
PMCID: 7582902
Citations: 28
Influential citations: 2
Summary: The genes, pathways and metabolites identified for each HD stage can provide a better understanding of the mechanisms that become altered in each disease stage, leading to an improvement in clinical symptoms and hopefully a delay in the age of onset.
Evidence snippets:
Snippet 1 (score: 0.367) > HD is a monogenetic and incurable disease and at the same time its molecular manifestations remain highly complex and involve multiple cellular processes, genes, and metabolites, which needs to be investigated to understand HD pathology. Systems bioinformatics (SB) allows the integration of different biological omics data to better understand the biological pathways, mechanisms, genes and metabolites involved in HD and lead to possible therapeutic treatments and biomarker discovery. > SB is an interdisciplinary field which combines the research fields of systems biology and bioinformatics. SB allows the integration of biological data across the omics categories such a genomics, transcriptomics, proteomics, metabolomics, lipidomics, epigenomics and several types of omics data [7]. > A major approach in this direction is the generation and construction of biological networks representing each level of omics data and their integration in a layered network that permits the exchange of information between and within the layers. The goal is to reveal synergistic relationships among numerous factors rather than explore each entity individually. This data integration approach results in the construction of highly complex molecular interaction networks. The biological data, obtained through large-scale omics analysis can provide a better understanding into biological mechanisms and pathways and how a dysfunction in these mechanisms and pathways can cause the disease [7]. Furthermore, the emerging importance of biological network-based approaches, allows for potential biological and clinical applications by suggesting an intuitive and trustworthy approach to explore the biological and molecular complexity of a disease of interest [8]. > The metabolome is defined as the complete set of small chemical molecules found within a biological samples (urine, cerebrospinal fluid (CSF), serum, plasma), tissues and cells. Changes and interactions in gene and protein expression and the environment are directly revealed in the metabolome making it more chemically and physically complex than the genome, transcriptome and proteome. Metabolites are affected by the upstream influence of the genome, proteome, environmental and lifestyle factors, as well as medication and underlying diseases [9]. > Metabolomics is an omics category focused in the study of metabolites. Metabolites are defined as small biological and low molecular weight (<1500 Da) compounds, they are the end-products of metabolism [10].

[13] A Lifelike guided journey through the pathophysiology of pulmonary hypertension—from measured metabolites to the mechanism of action of drugs

Authors: Nathan Weinstein, Jørn Carlsen, S. Schulz, T. Stapleton, H. H. Henriksen et al.
Year: 2023
Venue: Frontiers in Cardiovascular Medicine
URL: https://www.semanticscholar.org/paper/0b2dc837dea11add7e2f67f06acf6280ac96a019
DOI: 10.1101/2023.11.21.23298782
PMID: 38845688
PMCID: 11153715
Citations: 6
Summary: The present study shows the power of mining knowledge graphs using Lifelike's diverse set of data analytics functionalities for developing knowledge-driven hypotheses on PH pathophysiological and drug mechanisms and their interactions.
Evidence snippets:
Snippet 1 (score: 0.365) > Despite substantial progress in the understanding of PH pathophysiology over the last years, the detailed mechanisms underlying PH remain elusive due to the complex interplay of dysregulated biological processes.Also, although the mechanisms of action of some drugs that have been successfully used for the treatment of PH have been proposed, certain drugs may show additional mechanisms of action that are yet to be identified.Understanding these additional mechanisms of action is crucial for the personalized and thus more effective treatment of PH patients.In this study, we aimed to generate detailed mechanistic hypotheses of pathophysiological processes in PH using our in-house developed software platform Lifelike.Importantly, we have focused our analyses on the potential effects of blood plasma metabolites from PH patients on pulmonary endothelial and smooth muscle cells.Moreover, we used Lifelike to investigate the mechanisms of action of existing and new drugs used for the treatment of PH in more detail.We have achieved this by analyzing metabolite data and receptor ligands on the curated database Reactome using graph algorithms, and by combining our software's additional data analytics functionalities, including statistical enrichment and semantic analysis of textual information from Lifelike's knowledge graph.Additionally, we validated, interpreted, and extended our results based on relevant existing literature.This entire process allowed us to explore the pathophysiology of PH and to propose the model shown in figure 3 and summarized in figure 6.Further, Lifelike allowed us to generate the hypotheses discussed in the following sections and shown in Tables 2 and 3. > Lifelike also enables the reader of a biology article to quickly find the molecules, diseases, and phenotypes that are discussed in the manuscript or included in the figures through entity recognition.For instance, genes detected in articles by Lifelike's entity recognition system can be used to create an enrichment table where the genes can be associated with biological processes, molecular functions, and cell structures by GO enrichment.This allows the reader to find context-specific information quickly, and to extend the knowledge beyond what is described in the article with other sources of information (Table 1 row 21) We encourage the reader to upload this manuscript in PDF format into Lifelike for improved reading and knowledge extraction capabilities.

[14] Serum metabolomics identified specific lipid compounds which may serve as markers of disease progression in patients with Alström and Bardet-Biedl syndromes

Authors: Krzysztof Jeziorny, Karolina Pietrowska, Julia Siemińska, E. Zmysłowska-Polakowska, A. Kretowski et al.
Year: 2023
Venue: Frontiers in Molecular Biosciences
URL: https://www.semanticscholar.org/paper/1a1d29801c10582356f9813c445fa88ea892e855
DOI: 10.3389/fmolb.2023.1251905
PMID: 38028552
PMCID: 10657895
Citations: 5
Summary: Patients with ALMS/BBS have altered lipid metabolism compared to controls or obese subjects, and as the disease progresses, they show elevated levels of lipid oxidation products, which may suggest increased oxidative stress.
Evidence snippets:
Snippet 1 (score: 0.362) > To date, no precise therapy has been found to inhibit the development of all components of both syndromes, and treatment is only symptomatic or targeted at particular disorders, including those of a central origin (Haws et al., 2020;Haws et al., 2021). > Due to the progressive nature of the observed symptoms, leading to shortened life expectancy of patients, it seems reasonable to look for markers of progression of ALMS and BBS syndromes. One of the promising methods may be metabolomics. > Metabolomics is a relatively new technology that enables the evaluation of metabolites-small molecules formed during metabolism, the precise identification of which provides insight into biological processes. This allows a better understanding of cellular mechanisms and links them to the phenotype of patients. > Metabolomics is gaining popularity and there are more and more attempts to demonstrate its usefulness in understanding the pathophysiology of diseases, especially rare diseases (Zmyslowska et al., 2017;Zacchia et al., 2020). > The aim of the study was to identify serum metabolites characteristic to ALMS and BBS and to correlate the identified compounds with clinical parameters and diseases progression.

[15] Investigating the impact of gut microbiota-derived metabolites on benign prostatic hyperplasia using network pharmacology approaches

Authors: Yuanzhao Xu, Lingyue An, Jiling Xie, Chenggong Luo, Heng Zhang et al.
Year: 2026
Venue: BMC Pharmacology & Toxicology
URL: https://www.semanticscholar.org/paper/197e46477cdeb6884c734497d818f92cac74e67f
DOI: 10.1186/s40360-025-01059-y
PMID: 41535879
PMCID: 12888338
Citations: 1
Summary: A network pharmacology approach is employed to elucidate the intricate “Microbiota-Substrate-Metabolite-Target” (M-S-M-T) network in Benign Prostatic Hyperplasia (BPH), identifying key hub genes (AKT1, IL-6, IL-1B), signaling pathways, and gut microbiota-derived metabolites (butyrate, propionate, TMAO) as central regulators.
Evidence snippets:
Snippet 1 (score: 0.361) > KEGG analysis serves as a powerful tool for delineating well-characterized biological pathways and predicting the functions of currently uncharacterized genes or proteins. This methodology provides critical insights into the regulatory mechanisms governing biological processes, thereby enhancing our comprehensive understanding of them. The results of the KEGG enrichment analysis could be systematically categorized into three major groups (Fig. 5A, 5B, and 5C): 1) Human Diseases, such as "Pathways in cancer" and "Inflammatory bowel disease". This does not imply that BPH is a type of cancer or intestinal disease, but rather reveals that BPH shares many key regulatory mechanisms of cell proliferation and inflammation with these diseases. Gut microbial metabolites influence the development and progression of both BPH and its comorbidities (e.g., diabetes, cardiovascular diseases) by regulating these pathways. 2) Organismal Systems, which are primarily enriched in the "Immune system". This again highlights the central role of immune dysregulation in BPH, and the intervention effect of gut microbial metabolites on BPH through regulating immune-related pathways. 3) Signal Transduction, which is the focus of our attention. Among these, the five major pathways-AGE-RAGE, Toll-like receptor, HIF-1, C-type lectin receptor, and PI3K/Akt-serve as critical bridges linking GM metabolites, core targets, and BPH pathophysiology. Figure 5D presents the pathway-target

[16] Computational drug discovery approaches identify mebendazole as a candidate treatment for autosomal dominant polycystic kidney disease

Authors: P. Brownjohn, A. Zoufir, Daniel J O’Donovan, Saatviga Sudhahar, A. Syme et al.
Year: 2024
Venue: Frontiers in Pharmacology
URL: https://www.semanticscholar.org/paper/a595e78572ca02b8cb2897bfc4a989a2b021b279
DOI: 10.3389/fphar.2024.1397864
PMID: 38846086
PMCID: 11154008
Citations: 5
Summary: It is determined that the anthelmintic mebendazole was a potent anti-cystic agent in human cellular and in vivo models of ADPKD, and is likely acting through the inhibition of microtubule polymerisation and protein kinase activity.
Evidence snippets:
Snippet 1 (score: 0.361) > Targets and molecules were ultimately filtered for validation based on biological and chemical insights, and the potential for clinical translation.Earlier this year, Wilk et al., 2023 applied a similar transcriptomic approach to us, in that case making use of publicly available transcriptomic datasets to create Pkd2-specific ADPKD disease signatures, from which signature reversion was sought from the Library of Integrated Network-based Cellular Signatures (LINCs) drug signature database in order to identify drug repurposing candidates.While one group has previously made use of a knowledge graph-based approach to prioritise preclinically active compounds with the highest chance of clinical translation (Malas et al., 2019), to our knowledge, the current study provides the first combined application of transcriptomic and machine-learning approaches to identify and prioritise putative treatments for ADPKD, and further deconvolute potential mechanisms of action for experimental validation. > In summary we report, using computational, in vitro and in vivo approaches, that the anthelmintic drug mebendazole ameliorates disease-relevant phenotypes in cellular and animal models of ADPKD.We further show that this effect is likely primarily due to the inhibitory effect of mebendazole on the polymerisation of microtubules, which underlie cellular processes important in ADPKD, including cell proliferation, transport, and cilia signalling, and extends previous work linking the importance of the microtubule network to ADPKD pathophysiology.We also describe the inhibitory profile of mebendazole on known and novel protein kinase targets, some of which have previously been implicated in ADPKD, suggesting mebendazole may be acting via polypharmacology to impact disease mechanisms.We acknowledge that further experimental efforts will be required to confirm the actions of mebendazole on these putative targets in relevant disease model systems.It would be particularly informative to investigate these mechanisms in dedicated in vivo studies, where the effects of mebendazole on a wider range of ADPKD-relevant cell types and phenotypes could be evaluated.

[17] Human Dermal Fibroblast: A Promising Cellular Model to Study Biological Mechanisms of Major Depression and Antidepressant Drug Response

Authors: P. Mesdom, R. Colle, É. Lebigot, S. Trabado, Eric Deflesselle et al.
Year: 2020
Venue: Current Neuropharmacology
URL: https://www.semanticscholar.org/paper/79368e365458486de96794333613c12a6063bf54
DOI: 10.2174/1570159X17666191021141057
PMID: 31631822
PMCID: 7327943
Citations: 16
Summary: This review highlights the great and still underused potential of HDF, which stands out as a very promising tool in the understanding of MDD and AD mechanisms of action.
Evidence snippets:
Snippet 1 (score: 0.360) > Background: Human dermal fibroblasts (HDF) can be used as a cellular model relatively easily and without genetic engineering. Therefore, HDF represent an interesting tool to study several human diseases including psychiatric disorders. Despite major depressive disorder (MDD) being the second cause of disability in the world, the efficacy of antidepressant drug (AD) treatment is not sufficient and the underlying mechanisms of MDD and the mechanisms of action of AD are poorly understood. Objective The aim of this review is to highlight the potential of HDF in the study of cellular mechanisms involved in MDD pathophysiology and in the action of AD response. Methods The first part is a systematic review following PRISMA guidelines on the use of HDF in MDD research. The second part reports the mechanisms and molecules both present in HDF and relevant regarding MDD pathophysiology and AD mechanisms of action. Results HDFs from MDD patients have been investigated in a relatively small number of works and most of them focused on the adrenergic pathway and metabolism-related gene expression as compared to HDF from healthy controls. The second part listed an important number of papers demonstrating the presence of many molecular processes in HDF, involved in MDD and AD mechanisms of action. Conclusion The imbalance in the number of papers between the two parts highlights the great and still underused potential of HDF, which stands out as a very promising tool in our understanding of MDD and AD mechanisms of action

[18] The Lamin Proteins in Nuclear Structure, Functions, and Laminopathies

Authors: Gan Zhao, Zi-Heng Chen, Caifeng Yang, Mingzheng Liu, Weiyong Wang et al.
Year: 2026
Venue: Cells
URL: https://www.semanticscholar.org/paper/9db8088d893cc5c3de80d3afda68b52e1cf501fc
DOI: 10.3390/cells15121051
PMID: 42346079
PMCID: 13296569
Citations: 1
Summary: Collectively, studies of lamin protein function reveal how the nucleus maintains its structures and functions, while studies of laminopathies demonstrate how nuclear dysfunction drives systemic disease and points toward mechanism-based therapies.
Evidence snippets:
Snippet 1 (score: 0.359) > Laminopathies represent a clinically diverse class of human diseases caused by mutations in genes encoding components of the nuclear lamina and associated nuclear envelope proteins. Here, we summarize the mutation sites, phenotypes, and underlying molecular mechanisms of laminopathies (Table 1). Although mutations in LMNA account for the majority of reported cases, disease-causing alterations in B-type lamins, particularly LMNB1, as well as mutations in other nuclear envelope proteins, also give rise to distinct laminopathy phenotypes [13,77]. The pathogenesis of laminopathies is explained through several interconnected mechanistic frameworks. The classical structural hypothesis attributes disease to compromised nuclear integrity and impaired mechanical signaling, leading to stress-induced cellular damage, particularly in striated muscle tissues [23]. In contrast, the "gene expression hypothesis" emphasizes that lamin mutations disrupt chromatin organization and intracellular signaling pathways, thereby altering transcriptional programs [12,119]. More recently, these perspectives have been integrated with models highlighting cellular senescence, stem cell exhaustion, and chronic inflammation as additional pathogenic contributors, especially in progeroid syndromes [112]. Current evidence suggests that these mechanisms are not mutually exclusive but operate within an interconnected and synergistic network that drives disease progression [120]. > In laminopathies, mutations affect structural components present in nearly all nucleated cells. Nevertheless, laminopathies exhibit marked tissue-specific vulnerability, predominantly affecting striated muscle, adipose tissue, peripheral nerves, or, in some cases, causing systemic premature aging [12,15]. This tissue selectivity likely arises from the interaction between a specific lamin mutation and the distinct mechanical demands, transcriptional programs, and developmental context of individual tissues [15,119]. Consequently, although laminopathies share common molecular roots, their clinical manifestations are highly system-oriented. > For this reason, laminopathies are conventionally classified according to the primary tissue or organ system affected, despite substantial phenotypic overlap among categories [14]. This classification provides a clinically practical framework while acknowledging that shared pathogenic mechanisms underlie seemingly distinct disease entities. > Striated muscle laminopathies represent a major disease category.

[19] Modeling psychiatric disorders: from genomic findings to cellular phenotypes

Authors: Anna Falk, Vivi M. Heine, A. Harwood, Patrick F. Sullivan, M. Peitz et al.
Year: 2016
Venue: Molecular Psychiatry
URL: https://www.semanticscholar.org/paper/235b41240d78140de7ab06a3ad8a7d0b1bdff1a5
DOI: 10.1038/mp.2016.89
PMID: 27240529
PMCID: 4995546
Citations: 83
Influential citations: 2
Summary: The challenges for modeling of psychiatric disorders, potential solutions and how iPSC technology can be used to develop an analytical framework for the evaluation and therapeutic manipulation of fundamental disease processes are critically reviewed.
Evidence snippets:
Snippet 1 (score: 0.359) > The key challenge for iPSC-based disease modeling is to identify one or more relevant cellular phenotypes that accurately represent the disease pathophysiology. Increasing numbers of reports have demonstrated that for many diseases specific pathophysiology can be captured in human iPSC-based disease models. These range from cardiovascular disease, 44,45 cancer, 46,47 ocular disease, 48,49 diabetes mellitus 50,51 and neurological disorders of the brain. 52,53 Can the same approach be applied to complex psychiatric disorders? > The problem is that almost all psychiatric disorders are characterized by clinical signs and symptoms, but lack independent verification from objective biomarkers. Thus, how might these clinical phenotypes manifest themselves in terms of cell behavior? The identity of robust cellular 'readouts', which typify any psychiatric disorder, is a crucial unsolved problem and an area of intense study 54 (Table 2). When satisfactorily answered, this will herald a new degree of biological objectivity and quantification for the study of psychiatric disorders. > The aim is to find a single or small number of cell phenotypes or parameters that strongly associate with psychiatric disorders, and establish a cellular profile characteristic of cells derived from the general patient population. Although a consensus set of cellular phenotypes for psychiatric disorder is yet to be established, we can define some of their desired characteristics. First, cellular phenotypes have to relate to the biological pathways identified by genetics. Second, although there are many risk genes in disparate biological pathways, at some level, phenotypes should converge onto a much smaller grouping. Third, phenotypes need to be quantifiable. Finally, to be useful for drug development cellular phenotypes should be reversed by pharmacological treatment, although not necessarily by drugs in current use. > Although human iPSC-based approaches underrepresent the complexity of the human central nervous system, cellular phenotypes are likely to lie more proximal to molecular disease mechanisms than phenotypes seen at the level of a tissue or organism, 55 and thus may bypass compensatory homeostatic (2) Gene expression profiles of SCZ human iPSC neurons identified altered expression of many components of the cyclic AMP and WNT signaling pathways.

[20] Clinical Phenotypes of Cardiovascular and Heart Failure Diseases Can Be Reversed? The Holistic Principle of Systems Biology in Multifaceted Heart Diseases

Authors: K. Lourida, G. Louridas
Year: 2022
Venue: Cardiogenetics
URL: https://www.semanticscholar.org/paper/3960806730c4c1115f527e22d6d0a76536570ec5
DOI: 10.3390/cardiogenetics12020015
Citations: 4
Influential citations: 1
Summary: Only by understanding the complexity of chronic heart diseases and explaining the interrelationship between different interconnected biological networks can the probability for clinical phenotypes reversal be increased.
Evidence snippets:
Snippet 1 (score: 0.358) > Treatment with ACEIs, ARBs, and β-blockers impedes deterioration of myocardial function as well as clinical deterioration caused by the deleterious impact of the compensatory systems [58,59]. Therefore, the therapy with ACEIs, ARBs, and β-blockers is the appropriate therapy to block LV remodeling and HF progression and reduce symptoms and/or mortality [55]. > In general, the HF syndrome demonstrates a modular construction with predictable behavior of functional clinical phenotypes having a strong impact on biological networks from epigenetic, cellular to regulatory systems [18]. The importance of individual genes for the pathogenesis and clinical progression of the HF syndrome is restricted to the hypertrophic and dilated cardiomyopathies. It seems that some HF patients have a complex multigenic inheritance, but the importance of individual genes is limited. In contrast, the significant role of epigenetics, proteomics, and metabolomics is increased; but, the complete genetic network system and the interactions between multiomics systems are still uncertain [60]. Multimodal systems that include genetic networks, multiomics, metabolic pathways, environmental factors, and sophisticated disease-related clinical networks are required to be integrated and provide a new holistic and realistic picture. > Significant breakthroughs have been made to understand many of the pathophysiological mechanisms of HFrEF but the natural pathophysiological history and clinical progression of HFpEF still remains inadequately defined [39]. The subclinical progression of pre-clinical diastolic dysfunction (PDD) of LV "to clinical phenotype of HFpEF and the further clinical progression to some more complex clinical models with multi-organ involvement . . . continue to be poorly understood" [40]. Prospective studies are expected to clarify the natural history and clinical progression of HFpEF and define the LV remodeling mechanisms involved. The pathophysiology of LV systolic dysfunction is different to the diastolic dysfunction, as systolic dysfunction is considered a disease of calcium handling and diastolic dysfunction is regarded as a disease of increased myofilament sensitivity to calcium [61][62][63].

Notes

This provider combines search_papers_by_relevance with snippet_search.
No synthesis or second-stage model call is performed.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	36
Resolved	36
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	36
On topic	22
Off topic	0

All extracted references resolved successfully.

Term Validation

No ontology term identifiers were found in this report.

Falcon ▸

Buschke–Ollendorff Syndrome: Disease Characteristics Research Report

Edison Scientific Literature 18 citations 2026-09-05T18:07:14.349992

Buschke–Ollendorff Syndrome: Disease Characteristics Research Report

Executive summary

Buschke–Ollendorff syndrome (BOS) is a rare autosomal-dominant genodermatosis/sclerosing bone dysplasia defined by connective-tissue nevi together with osteopoikilosis. It is usually caused by heterozygous germline loss-of-function variants in LEMD3, encoding the inner-nuclear-membrane protein MAN1. MAN1 normally restrains BMP and activin/TGF-β signaling through receptor-regulated SMADs; haploinsufficiency therefore perturbs connective-tissue and bone homeostasis. Typical disease is benign, variably expressed, and often recognized from childhood skin lesions or incidental periarticular “spotted bone” lesions on radiographs. No disease-modifying therapy or validated BOS-specific clinical trial exists; care is symptom-directed. (mumm2007deactivatinggermlinemutations pages 1-2, hellemans2004lossoffunctionmutationsin pages 1-2, frost2020modelingbasedboneformation pages 1-7, hellemans2004lossoffunctionmutationsin pages 4-5)

Knowledge-base field	Curated summary	Ontology / representative data	Evidence
Identity and identifiers	Buschke–Ollendorff syndrome (BOS) is a rare Mendelian genodermatosis and sclerosing bone dysplasia defined by connective-tissue nevi with osteopoikilosis. Melorheostosis may coexist, but sporadic melorheostosis is genetically distinct. Synonyms include dermatofibrosis lenticularis disseminata with osteopoikilosis and dermato-osteopoikilosis.	MONDO:0008157; OMIM/MIM 166700	(mumm2007deactivatinggermlinemutations pages 1-2, hellemans2004lossoffunctionmutationsin pages 1-2, korman2016mutationinlemd3 pages 1-2)
Defining phenotype	Usually asymmetrical, non-tender, flesh-colored to yellow papules, nodules, or cobblestone plaques representing elastoma, collagenoma, or mixed connective-tissue nevi. Radiographs show multiple small, round or ovoid, generally symmetric periarticular sclerotic bone islands, especially in epiphyses, metaphyses, pelvis, carpal bones, and tarsal bones.	Suggested HPO: Connective tissue nevus; Collagenoma; Osteopoikilosis (HP:0005681); Melorheostosis (HP:0005781); Arthralgia (HP:0002829); Joint contracture (HP:0001371)	(mumm2007deactivatinggermlinemutations pages 1-2, brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, tan2025clinicalandhistopathological pages 1-2)
Causal gene and inheritance	Heterozygous germline loss-of-function variants in LEMD3 (MAN1) cause autosomal-dominant BOS through haploinsufficiency. Expression is highly variable within families, and not every clinically affected family has an identifiable coding variant. No reliable genotype–phenotype correlation is established.	LEMD3; ENSG00000174106. Representative variants: c.1323C>A, p.Tyr441Ter; c.332_333insTC; c.1863G>A, p.Trp621Ter; c.2203C>T, p.Arg735Ter. Reported classes include nonsense, frameshift, splice-disrupting, and larger deletion variants.	(OpenTargets Search: Buschke-Ollendorff syndrome-LEMD3, korman2016mutationinlemd3 pages 2-4, mumm2007deactivatinggermlinemutations pages 1-2, steensel2008buschkeollendorfsyndromereport pages 1-2)
Mechanism	MAN1 is an integral inner-nuclear-membrane protein whose C-terminal region binds receptor-regulated SMADs. Loss of MAN1-mediated antagonism increases BMP and TGF-β/activin signaling. This plausibly promotes abnormal dermal extracellular-matrix accumulation and focal osteogenesis. Human bone biopsies support activation of bone-lining cells and modeling-based formation of compact lamellar bone, although the complete tissue-selective causal chain remains unresolved.	Suggested GO: inner nuclear membrane (GO:0005637); BMP signaling pathway (GO:0030509); TGF-β receptor signaling pathway (GO:0007179); SMAD protein signal transduction (GO:0060395); ossification (GO:0001503); extracellular-matrix organization (GO:0030198). Suggested CL: fibroblast (CL:0000057); osteoblast (CL:0000062).	(hellemans2004lossoffunctionmutationsin pages 1-2, hellemans2004lossoffunctionmutationsin pages 4-5, frost2020modelingbasedboneformation pages 1-7)
Onset and course	Connective-tissue nevi most often begin congenitally, in infancy, or during childhood, but delayed adult presentation occurs. Lesions may enlarge slowly. Osteopoikilosis is developmental, persistent, and commonly detected incidentally. Severity ranges from asymptomatic disease to uncommon pain, contracture, deformity, or restricted motion.	Suggested HPO onset: Congenital onset (HP:0003577); Infantile onset (HP:0003593); Childhood onset (HP:0011463). Course: chronic and usually stable or slowly progressive.	(mumm2007deactivatinggermlinemutations pages 1-2, korman2016mutationinlemd3 pages 1-2, tan2025clinicalandhistopathological pages 1-2)
Diagnosis	Diagnosis integrates dermatologic examination, characteristic plain radiographs, family history, and, when needed, skin biopsy and germline LEMD3 sequencing with deletion/duplication analysis. Histology may show thick disorganized elastic fibers, dense collagen bundles, mixed lesions, or mucin. Important differentials include isolated osteopoikilosis, osteoblastic metastases, mastocytosis, tuberous-sclerosis shagreen patch, familial or eruptive collagenoma, papular elastorrhexis, morphea, and melorheostosis.	Genetic marker: pathogenic or likely pathogenic germline LEMD3 variant. Suggested procedures: radiography; skin biopsy; sequence analysis; copy-number analysis.	(brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, tan2025clinicalandhistopathological pages 1-2, steensel2008buschkeollendorfsyndromereport pages 1-2, mumm2007deactivatinggermlinemutations pages 1-2)
Epidemiology	Frequently cited occurrence is approximately 1 in 20,000, but this is an estimate rather than a robust population-registry measurement. BOS-specific incidence, sex ratio, ethnic differences, carrier frequency, and geographic variation remain undetermined.	Rare disease; no validated population-stratified prevalence dataset	(brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, frost2020modelingbasedboneformation pages 1-7, tan2025clinicalandhistopathological pages 1-2)
Treatment and prognosis	No disease-modifying or genotype-directed therapy is established. Most asymptomatic patients require reassurance and observation. Management is individualized and may include analgesia or physical therapy for musculoskeletal symptoms, dermatologic procedures for troublesome nevi, and orthopedic intervention for substantial deformity, contracture, or impingement. Prognosis and life expectancy are generally normal because typical osteopoikilosis and skin lesions are benign.	Suggested NCIT intervention concepts: Observation; Genetic Counseling; Analgesic Therapy; Physical Therapy; Surgical Procedure	(brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, korman2016mutationinlemd3 pages 2-4)
Evidence gaps	No validated protective or environmental risk factors, gene–environment interaction, epigenomic signature, circulating biomarker, formal staging system, disease-specific quality-of-life instrument, pharmacogenomic guidance, approved targeted therapy, or relevant interventional clinical trial was identified. No faithful animal model recapitulates the combined human skin-and-bone phenotype. Inconsistent fibroblast signaling and absent genotype–phenotype correlation limit mechanistic prediction.	Research priorities: longitudinal natural-history registry; standardized phenotyping; lesional single-cell and spatial profiling; functional variant assays; tissue-specific models	(korman2016mutationinlemd3 pages 4-6, korman2016mutationinlemd3 pages 2-4, hellemans2004lossoffunctionmutationsin pages 4-5)

Table: A knowledge-base-ready synopsis of BOS identity, phenotype, genetics, mechanism, diagnosis, course, management, and major evidence gaps, with ontology suggestions and representative LEMD3 variants.

Evidence scope and currency

The strongest evidence comprises the 2004 gene-discovery study, subsequent familial sequencing studies, human cellular assays, and a 2020 two-patient bone-biopsy study. The 2023–2024 literature mainly updates the wider biology of high-bone-mass and BMP/TGF-β disorders rather than providing new BOS cohorts. A 2024 neuropsychological report is a single preprint and cannot establish neurodevelopmental manifestations as part of classic BOS. A small 2025 dermatology case series is included as post-2024 supporting evidence because it supplies unusually useful onset and histopathology data, but its estimates should not be generalized as population frequencies. (frost2020modelingbasedboneformation pages 1-7, tan2025clinicalandhistopathological pages 1-2)

1. Disease information

Definition and identifiers

BOS is the syndromic coexistence of connective-tissue nevi—elastic, collagenous, or mixed—with osteopoikilosis, a developmental sclerosing bone dysplasia characterized by multiple small bone islands. Melorheostosis can occasionally coexist, but isolated sporadic melorheostosis is not synonymous with BOS. (mumm2007deactivatinggermlinemutations pages 1-2, hellemans2004lossoffunctionmutationsin pages 1-2)

MONDO: MONDO:0008157.
OMIM/MIM: 166700.
Causal disease-target association: Open Targets identifies LEMD3 (ENSG00000174106) as the single associated target, based on five evidence records and literature including PMID 15489854 and 17223882. (OpenTargets Search: Buschke-Ollendorff syndrome-LEMD3)
Orphanet: BOS is represented in Orphanet, but an exact ORPHA number was not independently recoverable from the retrieved primary literature; it should be verified directly against the current Orphanet nomenclature release before ingestion.
ICD-10/ICD-11: No retrieved evidence established a dedicated BOS code. In practice it may be represented under broader congenital skin/connective-tissue or osteodysplasia categories; a broad code should not be treated as disease-specific.
MeSH: No dedicated BOS descriptor was verified; “Osteopoikilosis” and broader connective-tissue-nevus terminology are commonly used for indexing.

Synonyms: Buschke–Ollendorff syndrome; Buschke-Ollendorf syndrome; dermato-osteopoikilosis; dermatofibrosis lenticularis disseminata with osteopoikilosis; osteopoikilosis with connective-tissue nevi. Juvenile elastoma and dermatofibrosis lenticularis disseminata describe cutaneous components rather than exact synonyms in every patient. (mumm2007deactivatinggermlinemutations pages 1-2, hellemans2004lossoffunctionmutationsin pages 1-2, steensel2008buschkeollendorfsyndromereport pages 1-2)

This report summarizes aggregated disease-level resources and published patients/families, not EHR-derived individual-level data.

Primary-literature definition: the foundational study described BOS as an autosomal-dominant disorder combining osteopoikilosis with “disseminated connective-tissue nevi.” Publication: 17 October 2004; DOI: https://doi.org/10.1038/ng1453; PMID: 15489854. (hellemans2004lossoffunctionmutationsin pages 1-2)

2. Etiology

Causal factors and genetic risk

The principal cause is a heterozygous germline loss-of-function LEMD3 variant, producing MAN1 haploinsufficiency. Reported classes include nonsense, frameshift, splice-disrupting, and larger deletion variants. Representative familial variants include c.1323C>A, p.Tyr441Ter; c.332_333insTC; and c.1863G>A, reported as p.Trp620Ter or p.Trp621Ter because of transcript/numbering differences. (mumm2007deactivatinggermlinemutations pages 1-2, steensel2008buschkeollendorfsyndromereport pages 1-2, korman2016mutationinlemd3 pages 4-6, korman2016mutationinlemd3 pages 2-4)

Family history is therefore the major risk factor. Each child of a heterozygous affected person has a theoretical 50% transmission probability, but phenotype cannot be predicted reliably because penetrance of individual components and expressivity are variable. Relatives carrying the same variant may have BOS, isolated osteopoikilosis, skin lesions alone, or minimal/no recognized manifestations. (korman2016mutationinlemd3 pages 2-4, hellemans2004lossoffunctionmutationsin pages 1-2)

Environmental, infectious, and lifestyle factors

No toxin, radiation exposure, infection, diet, smoking behavior, occupation, or other environmental exposure is established as a cause or modifier of classic BOS. Trauma may bring a skeletal lesion to clinical attention but is not demonstrated to cause the Mendelian disorder. No validated gene–environment interaction has been reported.

Protective factors

No protective LEMD3 allele, modifier locus, lifestyle intervention, diet, or prophylactic exposure has been demonstrated. Population-database rarity of loss-of-function alleles is useful for pathogenicity assessment but is not evidence of a protective genotype.

3. Phenotypes

Core manifestations

Phenotype	Type and characteristics	Onset/course and frequency evidence	Suggested HPO
Connective-tissue nevi	Non-tender flesh-colored, yellowish, or red papules/nodules; may coalesce into cobblestone plaques. Histologically elastoma, collagenoma, or mixed lesions	Commonly congenital, infantile, or childhood; usually slowly enlarging and persistent. A 2025 small series reported 23% before age 1 and one onset at 47 years, but this is not a population estimate	Connective tissue nevus; collagenoma; abnormal elastic tissue
Osteopoikilosis	Multiple 1–5-mm round/ovoid, generally symmetric periarticular sclerotic foci, especially epiphyses/metaphyses, pelvis, carpus, and tarsus	Developmental and lifelong; often asymptomatic and incidentally detected	HP:0005681 Osteopoikilosis
Melorheostosis	Asymmetric flowing cortical hyperostosis, classically “dripping candle wax”	Uncommon in BOS; may cause pain, deformity, or restricted motion. Sporadic melorheostosis is genetically distinct	HP:0005781 Melorheostosis
Musculoskeletal pain/arthralgia	Subjective pain around involved bones or joints	Minority manifestation; osteopoikilosis literature estimates arthralgia/synovitis in approximately 15–20%, but this cannot be assumed to be BOS-specific	HP:0002829 Arthralgia; bone pain
Contracture/deformity	Restricted motion, skin contracture, thumb or limb deformity in severe localized disease	Rare and variable; may progress sufficiently to require orthopedic correction	HP:0001371 Joint contracture; limited joint mobility
Dermal fibrosis/morphea-like change	Dense collagen, sclerotic plaques, occasionally lichen-sclerosus-like change	Rare association; adult-onset generalized morphea has been reported but is not a defining phenotype	Scleroderma; abnormality of skin morphology

The osteopoikilosis pattern and childhood skin lesions are documented in multiple human families. One infant developed a firm abdominal eruption at three months, while another had infantile lesions that became widespread and pruritic by age five. (mumm2007deactivatinggermlinemutations pages 1-2, korman2016mutationinlemd3 pages 1-2, tan2025clinicalandhistopathological pages 1-2)

Histopathology and laboratory findings

Skin biopsies are heterogeneous: elastic fibers may be thickened, enlarged, and haphazard; collagenomas show hypocellular dense interlacing collagen; mixed lesions and interstitial mucin occur. Thus, a normal or non-classic elastic stain does not exclude BOS. Bone biopsy can show thickened cortex/trabeculae and compact lamellar sclerotic nodules without woven bone. Routine blood chemistry and bone-turnover markers are usually normal. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, frost2020modelingbasedboneformation pages 1-7, tan2025clinicalandhistopathological pages 1-2)

Neurobehavioral phenotype

Intellectual disability, attention, language, coordination, and learning difficulties were described in a 2024 single-child preprint. This is hypothesis-generating only. Developmental delay is better established in large 12q14 deletions involving additional genes than in isolated heterozygous LEMD3 loss of function; neurodevelopmental findings should therefore trigger evaluation for a larger copy-number variant or another diagnosis.

Quality of life

No BOS-specific EQ-5D, SF-36, PROMIS, or validated natural-history study was found. Most patients have little functional impairment, but visible nevi may create cosmetic/psychosocial burden, while pain, contracture, deformity, or restricted motion can affect mobility and daily activities. Severe impairment is case-based rather than quantified. (mumm2007deactivatinggermlinemutations pages 1-2, brodbeck2016thebuschke–ollendorffsyndrome pages 1-3)

4. Genetic and molecular information

Gene and protein

Gene: LEMD3, approved symbol; aliases MAN1 and LEM domain-containing protein 3.
Genomic locus: chromosome 12q14 region.
Ensembl: ENSG00000174106. (OpenTargets Search: Buschke-Ollendorff syndrome-LEMD3)
Protein: approximately 60-kDa integral inner-nuclear-membrane protein containing a LEM domain, two transmembrane segments, and a C-terminal SMAD-interacting/RNA-recognition-like region. (korman2016mutationinlemd3 pages 1-2, korman2016mutationinlemd3 pages 4-6)

Variant interpretation

Truncating variants that remove the C-terminal SMAD-binding region are consistent with loss of function and haploinsufficiency. For example, c.1863G>A p.Trp620/621Ter is predicted to remove the second transmembrane helix, DNA-binding region, and R-SMAD-interacting domain. Functional experiments showed that disease-associated truncating variants failed to suppress TGF-β signaling. (korman2016mutationinlemd3 pages 4-6, hellemans2004lossoffunctionmutationsin pages 4-5)

Variant classification should nevertheless be performed under ACMG/AMP criteria using the correct transcript, segregation, population frequency, predicted nonsense-mediated decay, and ClinVar assertions. Exact gnomAD frequencies were not present in the retrieved literature and should be queried variant by variant; pathogenic truncating alleles are expected to be very rare or absent. The causal variants are constitutional/germline, not established somatic drivers. No obligatory somatic “second hit” was detected in sampled BOS skin fibroblasts. (hellemans2004lossoffunctionmutationsin pages 1-2)

Genotype–phenotype relationship and modifiers

No reliable genotype–phenotype correlation exists. Identical variants can produce isolated osteopoikilosis, full BOS, or highly variable skin and skeletal involvement. No validated modifier gene, protective allele, anticipation, founder mutation, or epigenetic signature is known. Large 12q14 deletions may produce additional short-stature or neurodevelopmental phenotypes because neighboring genes are deleted; these are contiguous-gene disorders, not ordinary BOS.

5. Environmental information

Environmental toxins, pollution, radiation, occupational exposures, diet, exercise, alcohol, smoking, and infectious agents have no demonstrated etiologic role. BOS is neither contagious nor zoonotic. Environmental avoidance cannot prevent a constitutional LEMD3 variant. Symptom-sensitive activity modification may be appropriate for painful orthopedic disease, but this is tertiary management rather than primary prevention.

6. Mechanism and pathophysiology

Ordered causal chain

A heterozygous germline loss-of-function variant in LEMD3 leads to reduced functional MAN1 dosage at the inner nuclear membrane. (hellemans2004lossoffunctionmutationsin pages 1-2, hellemans2004lossoffunctionmutationsin pages 4-5)
Loss of the MAN1 C-terminal SMAD-interacting function leads to reduced binding/sequestration or regulation of receptor-activated SMAD1/2/3 and reduced cooperation with pathway-terminating machinery. (korman2016mutationinlemd3 pages 4-6, hellemans2004lossoffunctionmutationsin pages 4-5)
Reduced MAN1 antagonism results in increased or prolonged BMP and activin/TGF-β transcriptional signaling; disease-associated truncations fail to suppress TGF-β-responsive reporters. (steensel2008buschkeollendorfsyndromereport pages 1-2, hellemans2004lossoffunctionmutationsin pages 4-5)
Bone branch: dysregulated BMP/TGF-β signaling in osteogenic-lineage cells is inferred to lead to focal activation of bone-lining/osteoblast cells and modeling-based lamellar bone formation. (frost2020modelingbasedboneformation pages 1-7)
This focal modeling results in compact lamellar sclerotic nodules and radiographic osteopoikilosis; melorheostosis-like hyperostosis occurs less often. (frost2020modelingbasedboneformation pages 1-7)
Skin branch: dysregulated TGF-β/BMP signaling in dermal fibroblast/connective-tissue lineages is inferred to lead to altered collagen, elastic-fiber, and mucin deposition. Direct consistency across BOS fibroblast experiments is incomplete. (korman2016mutationinlemd3 pages 2-4, tan2025clinicalandhistopathological pages 1-2, korman2016mutationinlemd3 pages 4-6)
Extracellular-matrix accumulation results in collagenoma, elastoma, mixed connective-tissue nevi, and occasional fibrotic contracture. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, tan2025clinicalandhistopathological pages 1-2)

Molecular and cellular detail

The strongest functional evidence is from human/cell-line experiments. The MAN1 C terminus binds the MH2 domains of SMAD1 and SMAD2. Overexpressed MAN1 reduced BMP4-induced SMAD6, SMAD7, ID2, and ID3 expression in HEK293T cells and suppressed a TGF-β-responsive reporter in HepG2 cells; pathogenic truncations did not. An affected person’s fibroblasts showed haploinsufficiency and increased ID3 after TGF-β stimulation. However, other fibroblast studies did not consistently reproduce pathway changes, so tissue specificity remains unresolved. (korman2016mutationinlemd3 pages 4-6, hellemans2004lossoffunctionmutationsin pages 4-5)

The 2020 human histomorphometry study found normal overall remodeling but focal replacement of trabecular architecture by modeling-based compact lamellar bone, supporting bone-lining-cell activation rather than generalized high turnover. In two women, bone-turnover markers and lumbar BMD were normal, hip BMD was higher, and NaF-PET/CT showed irregular skeletal uptake. The tiny sample precludes prevalence or prognostic inference. DOI: https://doi.org/10.1016/j.bone.2020.115313, June 2020. (frost2020modelingbasedboneformation pages 1-7)

Ontology suggestions

GO biological process: GO:0030509 BMP signaling pathway; GO:0007179 TGF-β receptor signaling pathway; GO:0060395 SMAD protein signal transduction; GO:0001503 ossification; GO:0045778 positive regulation of ossification; GO:0030198 extracellular-matrix organization.
GO cellular component: GO:0005637 nuclear envelope; inner nuclear membrane; nucleus.
Cell Ontology: CL:0000057 fibroblast; CL:0000062 osteoblast; bone-lining cell; CL:0000137 osteocyte; mesenchymal stromal cell.

No BOS-specific transcriptomic, proteomic, metabolomic, lipidomic, single-cell, spatial-transcriptomic, multi-omic, or CRISPR-screen dataset was identified. These are major research gaps rather than negative biological findings.

7. Anatomical structures affected

Primary organs: skin and skeleton. Skin lesions favor trunk, abdomen, buttocks, thighs, and extremities and are often asymmetric. Skeletal lesions favor cancellous bone around joints—epiphyses/metaphyses of long bones, pelvis, carpal and tarsal bones. (mumm2007deactivatinggermlinemutations pages 1-2, tan2025clinicalandhistopathological pages 1-2)

Tissue/cell level: dermal connective tissue, fibroblasts, collagen and elastic-fiber matrix; trabecular/cortical bone, bone-lining cells, osteoblast lineage, and osteocytes. Bone marrow failure is not characteristic, distinguishing BOS from severe osteopetrosis. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, frost2020modelingbasedboneformation pages 1-7)

Subcellular level: MAN1 resides in the inner nuclear membrane/nuclear envelope, where its nucleoplasmic C terminus regulates SMAD signaling. (korman2016mutationinlemd3 pages 1-2, hellemans2004lossoffunctionmutationsin pages 4-5)

Suggested anatomy terms include UBERON:0002097 skin of body, dermis, bone tissue, appendicular skeleton, pelvis, carpal bone, and tarsal bone. Disease is commonly bilaterally/symmetrically distributed in bone but cutaneous disease can be markedly asymmetric; melorheostosis is usually segmental/asymmetric.

8. Temporal development

BOS is a chronic developmental disorder. Skin lesions most often arise congenitally, in infancy, or childhood, then remain stable or enlarge slowly; delayed adult cutaneous presentation is documented. Osteopoikilosis is lifelong and may not be found until an unrelated radiograph. There is no accepted staging system, end stage, relapsing-remitting pattern, or critical therapeutic window. (mumm2007deactivatinggermlinemutations pages 1-2, korman2016mutationinlemd3 pages 1-2, tan2025clinicalandhistopathological pages 1-2)

Spontaneous clearance is not a recognized general pattern. Treatment may improve symptoms or remove individual lesions but does not reverse the constitutional predisposition. Earlier recognition is valuable chiefly to avoid biopsy or oncologic workup of benign bone islands and to enable family counseling. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3)

9. Inheritance and population

Inheritance

Inheritance is autosomal dominant, with variable penetrance of skin and skeletal components and marked intrafamilial expressivity. Anticipation is not reported. Germline mosaicism is theoretically possible for any de novo variant but is not an established recurrent BOS mechanism. Consanguinity is not a risk factor for this dominant disorder. (korman2016mutationinlemd3 pages 2-4, mumm2007deactivatinggermlinemutations pages 1-2, hellemans2004lossoffunctionmutationsin pages 1-2)

Epidemiology

The frequently cited occurrence is approximately 1 in 20,000 (about 5 per 100,000), but this is an imprecise estimate rather than a modern registry-derived BOS prevalence. BOS-specific incidence, sex ratio, age distribution, carrier frequency, ethnic enrichment, founder effects, and geographic variation remain unknown. Ascertainment is probably incomplete because osteopoikilosis is often asymptomatic and skin findings can be subtle or absent. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, frost2020modelingbasedboneformation pages 1-7, tan2025clinicalandhistopathological pages 1-2)

10. Diagnostics

Practical diagnostic approach

Clinical examination: document connective-tissue papules, nodules, plaques, distribution, pain, contracture, and family history.
Plain radiographs: hands/wrists, pelvis, knees, ankles, or symptomatic sites usually show numerous small, homogeneous, symmetric periarticular bone islands. CT can define atypical lesions; routine PET/MRI is unnecessary in typical asymptomatic disease.
Skin biopsy: reserve for atypical lesions; use routine histology plus elastic-fiber stains. Collagenous, elastic, mixed, or mucin-rich findings are possible. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, tan2025clinicalandhistopathological pages 1-2)
Genetic confirmation: sequence LEMD3 coding exons and splice boundaries; contemporary testing should add deletion/duplication analysis. Familial studies historically used blood-derived DNA PCR/Sanger sequencing. A negative coding test does not categorically exclude a convincing phenotype. (steensel2008buschkeollendorfsyndromereport pages 1-2, korman2016mutationinlemd3 pages 2-4, mumm2007deactivatinggermlinemutations pages 1-2)
Broader testing: use a sclerosing-bone-dysplasia panel or WES/WGS when phenotype is atypical or LEMD3 testing is negative. Use chromosomal microarray when short stature, developmental delay, congenital anomalies, or dysmorphism suggests a 12q14 deletion. Karyotype, FISH, mitochondrial testing, and repeat-expansion testing are not routine.

There is no validated blood/urine biomarker, enzyme assay, electrophysiologic test, liquid biopsy, or omics diagnostic. Routine bone chemistry and turnover markers may be normal. (frost2020modelingbasedboneformation pages 1-7)

Differential diagnosis

Isolated osteopoikilosis: same skeletal pattern without connective-tissue nevi.
Osteoblastic metastases: generally irregular/asymmetric, axial-predominant, and clinically contextual; unlike the uniform periarticular distribution of osteopoikilosis.
Osteopathia striata/osteopetrosis: linear striations or generalized dense bone rather than discrete bone islands.
Melorheostosis: flowing cortical hyperostosis; sporadic cases generally lack germline LEMD3 variants. (mumm2007deactivatinggermlinemutations pages 1-2)
Tuberous-sclerosis shagreen patch, familial/eruptive collagenoma, nevus anelasticus, papular elastorrhexis, and pseudoxanthoma elasticum: distinguished by systemic findings, lesion morphology, histology, radiographs, and genetics.
Morphea/systemic sclerosis: inflammatory/sclerotic evolution, autoantibodies, Raynaud phenomenon, sclerodactyly, or organ involvement support alternatives; BOS nevi are hamartomatous. Negative systemic-sclerosis serology and absence of sclerodactyly aided one reported differential. (korman2016mutationinlemd3 pages 1-2)

No formal society diagnostic criteria or population/newborn screening program exists. Cascade clinical and genetic evaluation is appropriate after identifying a familial pathogenic variant.

11. Outcome and prognosis

Typical BOS is benign and does not appear to shorten life expectancy. No disease-specific mortality, five-/ten-year survival statistic, or excess cancer risk is established. Most morbidity is cosmetic or orthopedic. Complications include pain, joint restriction, contracture, deformity, nerve or joint impingement when melorheostosis is present, and diagnostic harm from mistaking bone islands for metastases. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3, frost2020modelingbasedboneformation pages 1-7)

No validated prognostic biomarker exists. Neither variant class nor lesion burden reliably predicts outcome. Melorheostosis, progressive contracture, and functional deformity indicate greater morbidity; isolated radiographic osteopoikilosis generally requires no intervention. Quality-of-life and disability outcomes have not been systematically quantified.

12. Treatment

Standard management

There is no approved disease-modifying, gene-directed, RNA, cell, or targeted therapy for BOS.

Observation and reassurance: preferred for asymptomatic skin and bone lesions; NCIT suggestions: Observation, Clinical Monitoring.
Pain management: simple analgesics/NSAIDs when clinically appropriate; NCIT: Analgesic Therapy.
Physical/occupational therapy: maintain range of motion and function in painful or contracture-prone disease; NCIT: Physical Therapy, Occupational Therapy.
Dermatologic treatment: excision or selected laser/procedural treatment may be considered for painful, function-limiting, or cosmetically distressing lesions, but recurrence/scarring and sparse outcome evidence should be discussed.
Orthopedic treatment: corrective osteotomy, excision/decompression, or contracture surgery only for major deformity, impingement, or functional loss. A reported thumb deformity improved after corrective osteotomy. NCIT: Surgical Procedure, Osteotomy. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3)
Morphea-like inflammatory disease: treat according to morphea severity rather than as routine BOS. One exceptional case received PUVA, calcitriol, hydroxychloroquine, mycophenolate, and topical agents with slow partial improvement; this is not evidence for treating ordinary BOS. (korman2016mutationinlemd3 pages 2-4)
Genetic counseling: explain 50% transmission risk and unpredictable expressivity; NCIT: Genetic Counseling.

No BOS-specific response rate, comparative treatment study, pharmacogenomic guidance, or relevant interventional NCT trial was identified. Bisphosphonate reports relate mainly to symptomatic melorheostosis and do not establish efficacy for osteopoikilosis or connective-tissue nevi.

13. Prevention

Primary prevention: no lifestyle, vaccine, drug, or environmental measure prevents a germline LEMD3 disorder. Reproductive options after identifying a familial pathogenic variant include prenatal diagnosis and preimplantation genetic testing, following nondirective counseling.

Secondary prevention: no population or newborn screening is recommended. Targeted cascade testing and radiographic/dermatologic evaluation can identify relatives and prevent unnecessary oncologic investigations.

Tertiary prevention: monitor symptomatic patients for pain, reduced motion, contracture, deformity, or nerve/joint impingement; intervene with rehabilitation or orthopedic care before fixed disability. Immunization, antimicrobial prophylaxis, and environmental remediation have no BOS-specific role.

14. Other species and natural disease

No well-established naturally occurring BOS equivalent was identified in companion animals, livestock, or wildlife. Accordingly, no breed association, VBO term, veterinary prevalence, cross-species transmission, or zoonotic potential can be assigned. LEMD3/MAN1 function is evolutionarily conserved, but experimental perturbation in other species should not be mislabeled as spontaneous BOS.

15. Model organisms

No model faithfully reproduces the combined human skin-nevus/osteopoikilosis phenotype.

Mouse: complete Lemd3 disruption causes severe developmental/vascular abnormalities and embryonic lethality, demonstrating essential MAN1 function but limiting its usefulness for adult BOS. Published work further indicates that a heterozygous gene-trap mouse does not reproduce human osteopoikilosis; species dosage sensitivity is therefore a major limitation.
Drosophila: MAN1 loss produces tissue-specific developmental defects and enhanced BMP-related phenotypes. These models establish conserved pathway antagonism but cannot model human bone or dermal connective-tissue architecture.
Zebrafish/Xenopus: MAN1 perturbation has been used to study BMP/TGF-β signaling and embryogenesis. Such developmental models are mechanistically informative but not validated BOS models.
Cellular systems: HEK293T and HepG2 reporter assays and patient fibroblasts demonstrate SMAD binding and pathway repression/loss of repression. Inconsistent patient-fibroblast results and lack of the bone microenvironment limit prediction of clinical severity. (korman2016mutationinlemd3 pages 4-6, hellemans2004lossoffunctionmutationsin pages 4-5)
Human tissue model: the two-patient 2020 bone-biopsy study is presently more disease-proximal than most animal work, implicating modeling-based lamellar bone formation and activated bone-lining cells. (frost2020modelingbasedboneformation pages 1-7)

Priority models include isogenic patient-derived iPSC osteoblast/fibroblast systems, tissue-specific heterozygous knock-in mice, and skin–bone organoid or spatial single-cell studies.

Key publications and direct abstract-level statements

Hellemans et al., Nature Genetics, 17 October 2004. “Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis.” DOI: https://doi.org/10.1038/ng1453; PMID: 15489854. Functional evidence showed MAN1 interaction with BMP- and activin/TGF-β-activated SMADs and antagonism of both pathways. (hellemans2004lossoffunctionmutationsin pages 1-2, hellemans2004lossoffunctionmutationsin pages 4-5)
Mumm et al., Journal of Bone and Mineral Research, February 2007. The study’s central conclusion was that deactivating germline LEMD3 mutations cause osteopoikilosis and BOS “but not sporadic melorheostosis.” DOI: https://doi.org/10.1359/jbmr.061102; PMID: 17223882. (mumm2007deactivatinggermlinemutations pages 1-2)
Brodbeck et al., BMC Research Notes, June 2016. Abstract conclusion: in atypical osteocutaneous presentations, the authors recommended LEMD3 screening and emphasized that correct diagnosis can spare “expensive investigations” and provide reassurance about the disease’s benign nature. DOI: https://doi.org/10.1186/s13104-016-2095-2. (brodbeck2016thebuschke–ollendorffsyndrome pages 1-3)
Frost et al., Bone, June 2020. Human biopsies supported modeling-based conversion of trabecular to compact lamellar bone in sclerotic areas. DOI: https://doi.org/10.1016/j.bone.2020.115313. (frost2020modelingbasedboneformation pages 1-7)
Tan et al., Acta Dermato-Venereologica, 8 April 2025. This recent small series broadened the recognized histology to collagenoma, elastoma, mixed lesions, and mucin deposition and documented onset from infancy to late adulthood. DOI: https://doi.org/10.2340/actadv.v105.42531. (tan2025clinicalandhistopathological pages 1-2)

Knowledge-base cautions

The often-quoted 1:20,000 figure is not a robust registry prevalence; feature percentages from small case series should not be interpreted as penetrance estimates. Classic BOS should not automatically include intellectual disability, generalized morphea, or sporadic melorheostosis. A pathogenic LEMD3 variant strongly supports diagnosis, but variable expression and occasional mutation-negative families mean that genotype must be interpreted with the osteocutaneous phenotype. The mechanistic link from enhanced SMAD signaling to tissue-selective lesions remains partly inferred, despite strong molecular evidence that MAN1 antagonizes BMP/TGF-β signaling. (korman2016mutationinlemd3 pages 2-4, hellemans2004lossoffunctionmutationsin pages 1-2, tan2025clinicalandhistopathological pages 1-2, korman2016mutationinlemd3 pages 4-6)

References

(mumm2007deactivatinggermlinemutations pages 1-2): Steven Mumm, Deborah Wenkert, Xiafang Zhang, William H McAlister, Richard J Mier, and Michael P Whyte. Deactivating germline mutations in lemd3 cause osteopoikilosis and buschke-ollendorff syndrome, but not sporadic melorheostosis. Feb 2007. URL: https://doi.org/10.1359/jbmr.061102, doi:10.1359/jbmr.061102. This article has 112 citations and is from a highest quality peer-reviewed journal.
(hellemans2004lossoffunctionmutationsin pages 1-2): Jan Hellemans, Olena Preobrazhenska, Andy Willaert, Philippe Debeer, Peter C M Verdonk, Teresa Costa, Katrien Janssens, Bjorn Menten, Nadine Van Roy, Stefan J T Vermeulen, Ravi Savarirayan, Wim Van Hul, Filip Vanhoenacker, Danny Huylebroeck, Anne De Paepe, Jean-Marie Naeyaert, Jo Vandesompele, Frank Speleman, Kristin Verschueren, Paul J Coucke, and Geert R Mortier. Loss-of-function mutations in lemd3 result in osteopoikilosis, buschke-ollendorff syndrome and melorheostosis. Oct 2004. URL: https://doi.org/10.1038/ng1453, doi:10.1038/ng1453. This article has 585 citations and is from a highest quality peer-reviewed journal.
(frost2020modelingbasedboneformation pages 1-7): M. Frost, E.T. Rahbek, C. Ejersted, P.F. Høilund-Carlsen, A. Bygum, J.S. Thomsen, C.M. Andreasen, T.L. Andersen, and A.L. Frederiksen. Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in buschke-ollendorff syndrome. a case study of two females with lemd3 variants. Jun 2020. URL: https://doi.org/10.1016/j.bone.2020.115313, doi:10.1016/j.bone.2020.115313. This article has 13 citations and is from a domain leading peer-reviewed journal.
(hellemans2004lossoffunctionmutationsin pages 4-5): Jan Hellemans, Olena Preobrazhenska, Andy Willaert, Philippe Debeer, Peter C M Verdonk, Teresa Costa, Katrien Janssens, Bjorn Menten, Nadine Van Roy, Stefan J T Vermeulen, Ravi Savarirayan, Wim Van Hul, Filip Vanhoenacker, Danny Huylebroeck, Anne De Paepe, Jean-Marie Naeyaert, Jo Vandesompele, Frank Speleman, Kristin Verschueren, Paul J Coucke, and Geert R Mortier. Loss-of-function mutations in lemd3 result in osteopoikilosis, buschke-ollendorff syndrome and melorheostosis. Oct 2004. URL: https://doi.org/10.1038/ng1453, doi:10.1038/ng1453. This article has 585 citations and is from a highest quality peer-reviewed journal.
(korman2016mutationinlemd3 pages 1-2): Benjamin Korman, Jun Wei, Anne Laumann, Polly Ferguson, and John Varga. Mutation in lemd3 (man1) associated with osteopoikilosis and late-onset generalized morphea: a new buschke-ollendorf syndrome variant. Case Reports in Dermatological Medicine, 2016:1-9, Jun 2016. URL: https://doi.org/10.1155/2016/2483041, doi:10.1155/2016/2483041. This article has 13 citations.
(brodbeck2016thebuschke–ollendorffsyndrome pages 1-3): Michael Brodbeck, Q. Yousif, P. A. Diener, M. Zweier, and J. Gruenert. The buschke–ollendorff syndrome: a case report of simultaneous osteo-cutaneous malformations in the hand. BMC Research Notes, Jun 2016. URL: https://doi.org/10.1186/s13104-016-2095-2, doi:10.1186/s13104-016-2095-2. This article has 11 citations and is from a peer-reviewed journal.
(tan2025clinicalandhistopathological pages 1-2): Yidong Tan, Jinxiang Yang, Xuanyi Chen, Zhirong Yao, and Jianying Liang. Clinical and histopathological characteristics of buschke–ollendorff syndrome: a case series. Acta Dermato-Venereologica, 105:adv42531, Apr 2025. URL: https://doi.org/10.2340/actadv.v105.42531, doi:10.2340/actadv.v105.42531. This article has 1 citations and is from a domain leading peer-reviewed journal.
(OpenTargets Search: Buschke-Ollendorff syndrome-LEMD3): Open Targets Query (Buschke-Ollendorff syndrome-LEMD3, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(korman2016mutationinlemd3 pages 2-4): Benjamin Korman, Jun Wei, Anne Laumann, Polly Ferguson, and John Varga. Mutation in lemd3 (man1) associated with osteopoikilosis and late-onset generalized morphea: a new buschke-ollendorf syndrome variant. Case Reports in Dermatological Medicine, 2016:1-9, Jun 2016. URL: https://doi.org/10.1155/2016/2483041, doi:10.1155/2016/2483041. This article has 13 citations.
(steensel2008buschkeollendorfsyndromereport pages 1-2): Michel van Geel, Valerie L.R.M. Verstraeten, G.P.H. Lucker, and Maurice A.M. van Steensel. Buschke-ollendorf syndrome: report of a case and a brief molecular overview. The Open Dermatology Journal, 02(1):05-08, Jan 2008. URL: https://doi.org/10.2174/1874372200802010005, doi:10.2174/1874372200802010005. This article has 0 citations.
(korman2016mutationinlemd3 pages 4-6): Benjamin Korman, Jun Wei, Anne Laumann, Polly Ferguson, and John Varga. Mutation in lemd3 (man1) associated with osteopoikilosis and late-onset generalized morphea: a new buschke-ollendorf syndrome variant. Case Reports in Dermatological Medicine, 2016:1-9, Jun 2016. URL: https://doi.org/10.1155/2016/2483041, doi:10.1155/2016/2483041. This article has 13 citations.

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Buschke–Ollendorff Syndrome: Disease Characteristics Research Report

Executive summary

Evidence scope and currency

1. Disease information

Definition and identifiers

2. Etiology

Causal factors and genetic risk

Environmental, infectious, and lifestyle factors

Protective factors

3. Phenotypes

Core manifestations

Histopathology and laboratory findings

Neurobehavioral phenotype

Quality of life

4. Genetic and molecular information

Gene and protein

Variant interpretation

Genotype–phenotype relationship and modifiers

5. Environmental information

6. Mechanism and pathophysiology

Ordered causal chain

Molecular and cellular detail

Ontology suggestions

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

Inheritance

Epidemiology

10. Diagnostics

Practical diagnostic approach

Differential diagnosis

11. Outcome and prognosis

12. Treatment

Standard management